High Doses Of Testosterone Research Articles

The influence of testosterone in the expression of androgen receptors in rat ovary

Event Abstract Back to Event The influence of testosterone in the expression of androgen receptors in rat ovary Ioannis Kyriakidis1*, Theodora Papamitsou2, Maria Dermentzopoulou-Theodoridou2, Ioannis Makaronidis1, Kyriaki Papadopoulou2, Fotios Tsanakalis1 and Paraskevi Papaioannidou1 1 Aristotle University of Thessaloniki, Department of Pharmacology, Greece 2 Aristotle University of Thessaloniki, Laboratory of Histology-Embryology and Anthropology, Greece Aim of our study was to investigate the localization of androgen receptors (ARs) in rat ovary, to examine the induction of ARs in the ovaries of female Wistar rats when administered with high dosages of testosterone, to measure any effects on weight and to record any toxic effects on the ovarian structure or function. For the purpose of this study female adult Wistar rats (6 weeks old, weighing from 150 to 200 gr, fed ad libitum) were used and separated in three groups. The first group received intramuscularly 25 mg of testosterone at the third day after menses and the second group received 12.5 mg of testosterone at also the same period. The third group was the control group. Ten days after the testosterone administration, euthanasia via ether was performed to the rats, while tissue samples from the ovaries were obtained, fixed and prepared for immunohistochemical study of ARs with polymerization. Ovaries in testosterone treated rats did not differ significantly with controls as regards their weight, while the first group -and moderately the second group- showed macroscopically hyperemia and hypertrophy. The expression of AR in the ovaries of rats who took high dose of testosterone was positive in various places of stromatic ovary cells and in some granule cells of secondary ovarian follicle with antrum. In the second group, AR staining was positive with increased expression in ovary’s germinal cells, in stromal cells and also in ovarian follicle’s granule cells and in radiata corona’s cells of the oocytes. In conclusion, AR expression was less positive in ovary’s follicle cells of the rats who took high doses of testosterone than in those who took lower doses. Keywords: Testosterone, Ovary, rat, androgen receptor Conference: 8th Southeast European Congress on Xenobiotic Metabolism and Toxicity - XEMET 2010, Thessaloniki, Greece, 1 Oct - 5 Oct, 2010. Presentation Type: Poster Topic: Xenobiotics and reproduction Citation: Kyriakidis I, Papamitsou T, Dermentzopoulou-Theodoridou M, Makaronidis I, Papadopoulou K, Tsanakalis F and Papaioannidou P (2010). The influence of testosterone in the expression of androgen receptors in rat ovary. Front. Pharmacol. Conference Abstract: 8th Southeast European Congress on Xenobiotic Metabolism and Toxicity - XEMET 2010. doi: 10.3389/conf.fphar.2010.60.00154 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 05 Mar 2011; Published Online: 04 Nov 2010. * Correspondence: Dr. Ioannis Kyriakidis, Aristotle University of Thessaloniki, Department of Pharmacology, Thessaloniki, Greece, kyriakidis@auth.gr Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Ioannis Kyriakidis Theodora Papamitsou Maria Dermentzopoulou-Theodoridou Ioannis Makaronidis Kyriaki Papadopoulou Fotios Tsanakalis Paraskevi Papaioannidou Google Ioannis Kyriakidis Theodora Papamitsou Maria Dermentzopoulou-Theodoridou Ioannis Makaronidis Kyriaki Papadopoulou Fotios Tsanakalis Paraskevi Papaioannidou Google Scholar Ioannis Kyriakidis Theodora Papamitsou Maria Dermentzopoulou-Theodoridou Ioannis Makaronidis Kyriaki Papadopoulou Fotios Tsanakalis Paraskevi Papaioannidou PubMed Ioannis Kyriakidis Theodora Papamitsou Maria Dermentzopoulou-Theodoridou Ioannis Makaronidis Kyriaki Papadopoulou Fotios Tsanakalis Paraskevi Papaioannidou Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD) reduces disinhibitory behavior in intact adult male rats treated with a high dose of testosterone

Anabolic androgenic steroids and high testosterone doses have been reported to induce impulsive behavior in man and behavioral disinhibition in rats. The purpose of the present study was to investigate whether aromatization of testosterone to estradiol is of importance for the behavioral disinhibiting effect of a high testosterone dose in adult male rats. Testosterone administered via five testosterone-filled silastic capsules implanted subcutaneously (s.c.) to non-castrated, group-housed rats for six days induced behavioral disinhibition in a modified Vogel's drinking conflict model and yielded supraphysiological serum levels of testosterone and increased accessory sex organ weights. Moreover, concurrent administration of the aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD; 60mg/kg/day s.c.) decreased behavioral disinhibition in testosterone-treated rats (without affecting accessory sex organ weights) while behavior was not significantly affected in sham-treated animals. Since some reports indicate that ATD, in addition to inhibit aromatase, also may affect the binding of testosterone to the androgen receptor, the effect of the non-steroidal androgen receptor antagonist flutamide was investigated. Flutamide treatment did not affect disinhibited behavior in testosterone-treated rats. However, in sham-treated animals, flutamide (50mg/kg/day) produced behavioral disinhibition. These results suggest that estradiol is of importance in the mechanisms underlying behavioral disinhibition in non-castrated rats treated with a high testosterone dose. Speculatively, aromatization may be involved in pro-impulsive effects of high testosterone doses in humans.

Safety and Efficacy of a Testosterone Metered-Dose Transdermal Spray for Treating Decreased Sexual Satisfaction in Premenopausal Women

It is not known whether premenopausal women who report low sexual satisfaction and have low circulating testosterone levels will benefit from testosterone therapy. To evaluate the effects of exogenous testosterone in premenopausal women reporting diminished sexual function. Randomized, double-blind, placebo-controlled, dose-ranging trial. 6 Australian medical centers. 261 women age 35 to 46 years who reported a decrease in satisfying sexual activity relative to their younger years and had a morning serum free testosterone level less than 3.8 pmol/L (<1.1 pg/mL). 3 different doses of testosterone administered by a metered-dose transdermal spray for 16 weeks or placebo. The primary outcome was the mean number of self-reported satisfactory sexual events (SSEs) over 28 days at week 16. The frequency of SSEs, total number of sexual events (every 4 weeks), scores from the modified Sabbatsberg Sexual Self-Rating Scale and the Psychological General Well-Being Index, and safety variables were also measured. The number of SSEs increased during the treatment period in the active treatment groups and the placebo group. The mean number of SSEs over 28 days at week 16 was statistically significantly greater for women treated with the intermediate dose of testosterone therapy (one 90-microL spray) than for women treated with placebo. The least-squares mean was 2.48 versus 1.70 SSEs, respectively (event rate ratio, 1.49 [95% CI, 1.01 to 2.18]; P = 0.04). The frequency of SSEs in women treated with low and high doses of testosterone did not differ from that in women who took placebo. The rate ratios based on the least-squares mean rates of SSEs during weeks 4 to 16 for each treatment group showed statistically significant or borderline significant increases in all testosterone groups compared with the placebo group. The rate ratios for the one 56-microL spray, one 90-microL spray, and two 90-microL sprays treatment groups were 1.34 (CI, 0.97 to 1.85; P = 0.081), 1.48 (CI, 1.07 to 2.06; P = 0.018), and 1.38 (CI, 1.00 to 1.92; P = 0.052), respectively. At week 16, 95% of women treated with the one 90-microL dose had a free testosterone level less than the upper limit of the reference range for women. The most frequently reported adverse event was hypertrichosis, which was dose-related and mostly confined to the application site. No clinically relevant changes in blood test values, serum biochemical variables, or vital signs occurred. The study duration was short, and the placebo effect was strong. A daily 90-microL dose of transdermal testosterone improves self-reported sexual satisfaction for premenopausal women with reduced libido and low serum-free testosterone levels by a mean of 0.8 SSE per month. The rate of SSEs with higher and lower testosterone doses did not differ from that with placebo.

Anabolic effects of testosterone are preserved during inhibition of 5α-reductase

At replacement doses, testosterone produces only modest increases in muscle strength and bone mineral density in older hypogonadal men. Although higher doses of testosterone are more anabolic, there is concern over increased adverse effects, notably prostate enlargement. We tested a novel strategy for obtaining robust anabolic effects without prostate enlargement. Orchiectomized (ORX) male rats were treated for 56 days with 1.0 mg testosterone/day, with and without 0.75 mg/day of the 5alpha-reductase inhibitor MK-434. Testosterone administration elevated the prostate dihydrotestosterone concentration and caused prostate enlargement. Both effects were inhibited by MK-434. ORX produced a catabolic state manifested in reduced food intake, blunted weight gain, reduced hemoglobin concentration, decreased kidney mass, and increased bone resorption, and in the proximal tibia there was both decreased cancellous bone volume and a decreased number of trabeculae. In soleus and extensor digitorum longus muscles, ORX reduced both the percentage of type I muscle fibers and the cross-sectional area of type 1 and 2 fibers. Testosterone administration caused a number of anabolic effects, including increases in food intake, hemoglobin concentration, and grip strength, and reversed the catabolic effects of ORX on bone. Testosterone administration also partially reversed ORX-induced changes in muscle fibers. In contrast to the prostate effects of testosterone, the effects on muscle, bone, and hemoglobin concentration were not blocked by MK-434. Our study demonstrates that the effects of testosterone on muscle and bone can be separated from the prostate effects and provides a testable strategy for combating sarcopenia and osteopenia in older hypogonadal men.

Localization of Fertility Factor SP22 to Specific Cell Types Within the Anterior Pituitary Gland

Sperm protein 22 (SP22) was recently identified in the anterior pituitary gland (AP) of male Golden Syrian hamsters using ion trap mass spectrometry. SP22 has been implicated in apoptosis, androgen receptor function, fertility, and ontogeny of early-onset Parkinson's disease. However, the role of SP22 in the pituitary has not been investigated. We cloned the cDNA for full-length SP22 from AP and posterior lobe (posterior pituitary and intermediate lobe) of the pituitary gland in adult male rats and Golden Syrian hamsters, confirming the presence of SP22 mRNA in the AP and posterior lobe. Because gonadal steroids are important regulators of AP function, and SP22 is associated with androgen receptor function, we used Western blots to compare SP22 in the AP of intact and orchidectomized male rats given placebo or a low or high dose of testosterone. SP22 did not differ with treatment, indicating that AP SP22 concentration was not regulated by testosterone. To localize SP22 to specific cells of the AP, mirror-image paraffin sections were labeled against SP22 and either luteinizing hormone (LH)beta, thyroid-stimulating hormone (TSH)beta, prolactin, adrenocorticotropic hormone (ACTH), or growth hormone (GH) using peroxidase-conjugated secondary antibody. Additional sections were colabeled with SP22 and one of the AP hormones using fluorescent secondary antibodies. SP22 colocalized in somatotropes and thyrotropes in rat and hamster. We identified SP22 in a small percentage of corticotropes, gonadotropes, and lactotropes. This is the first report that SP22 mRNA is present specifically in the AP, and SP22 is localized primarily in somatotropes and thyrotropes. SP22 may help regulate AP function and be particularly important for the control of GH and TSH secretion.

Testosterone Blunts Feedback Inhibition of Growth Hormone Secretion by Experimentally Elevated Insulin-Like Growth Factor-I Concentrations

The present study tests the hypothesis that a high dose of testosterone (Te) drives GH and IGF-I production, in part, by blunting autonegative feedback by the end-product peptide. To this end, we infused saline or recombinant human IGF-I (10 microg/kg.h iv for 6 h) in seven healthy men ages 51-72 yr after administration of placebo (Pl) and Te in randomized order. GH release was quantitated fasting before and after injection of GHRH (1 microg/kg). Statistical analyses disclosed that Te vs. Pl: 1) increased the mean concentration of GH from 0.15 +/- 0.045 to 0.48 +/- 0.11 microg/liter (P = 0.007) and IGF-I from 108 +/- 5.0 to 124 +/- 4.1 (P = 0.047) without altering GHRH-induced GH release; 2) elevated the GH nadir from 0.13 +/- 0.03 to 0.23 +/- 0.06 microg/liter (P < 0.05) in the control session and from 0.06 +/- 0.02 to 0.14 +/- 0.04 microg/liter (P = 0.038) during IGF-I infusion; 3) augmented GHRH-stimulated GH release from 3.0 +/- 0.56 (Pl) to 3.7 +/- 0.52 microg/liter (Te) (P < 0.05) during IGF-I infusion; and 4) did not influence estimated IGF-I kinetics. In summary, supplementation of a high dose of Te in middle-aged and older men attenuates IGF-I feedback-dependent inhibition of nadir and peak GH secretion. Both effects of Te differ from those reported recently for estradiol in postmenopausal women. Accordingly, we postulate that Te and estrogen modulate IGF-I negative feedback differentially.

High level of circulating testosterone abolishes decline in scent attractiveness in antigen-treated male mice

We hypothesized that a decrease in the attractiveness of odours from infected male mice, Mus musculus could be caused by either parasite-induced changes in host metabolism (parasite-dependent pathway) or activation of the immune defence system (immune-dependent pathway). Activation of the immune defence system by nonreplicated antigens (sheep red blood cells, SRBC) is sufficient for a decrease in both scent attractiveness and the concentration of plasma testosterone in male mice. Since the scent attractiveness of male mice depends on androgen levels, we studied the olfactory effect of SRBC in sham-operated, gonadectomized and testosterone-treated male mice of the outbred strain ICR. SRBC administration resulted in a decline in both sexual odour attractiveness and concentration of urinary proteins in sham-operated control males. The effect of SRBC on concentration of urinary proteins was abolished by stabilizing the testosterone level in gonadectomized and androgen-treated males. At the same time, only the high dose of testosterone was sufficient to maintain the scent attractiveness in SRBC-treated males at the pretreatment level.

Validation of a rapid yeast estrogen bioassay, based on the expression of green fluorescent protein, for the screening of estrogenic activity in calf urine

Previously we described the construction and properties of a rapid yeast bioassay stably expressing human estrogen receptor α (hERα) and yeast enhanced green fluorescent protein (yEGFP) in response to estrogens. In the present study, this yeast estrogen assay was validated as a qualitative screening method for the determination of estrogenic activity in calf urine. This validation was performed, according to EC decision 2002/657, which prescribes the determination of the detection capability ( CCβ), the specificity/selectivity and the stability/ruggedness/applicability. To determine these performance characteristics, twenty blank urine samples of 19-week-old calves were collected and spiked with 17β-estradiol (E2β) at 1 ng ml −1, diethylstilbestrol (DES) at 1 ng ml −1, 17α-ethynylestradiol (EE2) at 1 ng ml −1, α-zearalanol at 30 and 50 ng ml −1 or mestranol at 10 ng ml −1. Following enzymatic deconjugation and solid phase extraction, 100 μl equivalents of these blank and spiked urine samples were screened for estrogenic activity in a 96 well plate using the yeast estrogen bioassay. All of these low estrogen spiked urine samples could be distinguished from the blank samples as all spiked samples gave a signal above the determined decision limit CCα and the mean responses of the spiked samples were higher than the determined detection capability CCβ. As this CCβ criterion is met, these spiked samples have a lower than 5% probability to be classified as a false negative. The specificity of the method was determined with blank urine samples spiked with a high dose of testosterone or progesterone (1000 ng ml −1). No response to these substances was detected in the yeast estrogen bioassay. There was also no interference of a high dose of testosterone or progesterone on the response of a low dose of the estrogens. Stability of urine samples was checked with spiked urine samples that were kept frozen for up to 90 days, showing that urine samples could be stored at −20 °C for up to 60 days without changing the screening result of the assay. This method has been in routine use at RIKILT for more than one year.

Kennedy's disease: pathogenesis and clinical approaches.

Kennedy's disease, also known as spinal and bulbar muscular atrophy, is a progressive degenerative condition affecting lower motor neurons. It is one of nine neurodegenerative disorders caused by a polyglutamine repeat expansion. Affecting only men, Kennedy's disease is the only one of these conditions that follows an X-linked mode of inheritance. The causative protein in Kennedy's disease, with a polyglutamine expansion residing in the first N-terminal domain, is the androgen receptor. Research in this field has made significant advances in recent years, and with the increased understanding of pathogenic mechanisms, feasible approaches to treatments are being investigated. In Kennedy's disease research, the most significant issue to emerge recently is the role of androgens in exacerbating the disease process. On the basis of animal experiments, a viable hypothesis is that higher circulating levels of androgens in men could trigger the degeneration of motor neurons causing this disease, and that lower levels in heterozygous and homozygous women are protective. This is a major issue, as treatment of individuals affected by Kennedy's disease with testosterone has been considered a reasonable therapy by some neurologists. The rationale behind this approach relates to the fact that Kennedy's disease is accompanied by mild androgen insensitivity. It was therefore believed that treatment with high doses of testosterone might compensate for this loss of androgen action, with the added benefit of preventing muscle wasting. The current review provides an overview of recent advances in the field of Kennedy's disease research, including approaches to treatment.

In vitro effects of steroid hormones on IgM-secreting cells and IgM secretion in common carp ( Cyprinus carpio)

The effects of steroid hormones on in vitro IgM-secreting cells (IgMSC) and IgM secretion by lymphocytes of the lymphoid organs in common carp, Cyprinus carpio were examined by ELISPOT and ELISA assay, respectively. Cells isolated from peripheral blood (PB), spleen and head kidney were cultured for 12, 24 and 48 h either in the absence or in the presence of steroid hormones, i.e. cortisol, testosterone, 11-ketotestosterone (11-KT), and estradiol-17β (E 2) at doses of 1, 10 and 100 ng/ml. Cortisol reduced the IgMSC numbers and IgM secretion by cells from all organs. In addition, cortisol induced apoptosis in lymphocytes from all organs. High dose of testosterone showed tissue-specific functions; it reduced the number of IgMSC and amount of IgM secretion by cells from spleen and head kidney, but not in PB, though IgM secretion was suppressed. However, no effects of sex steroids were observed in this study. The results show that sex-specific steroid hormones may have no immunosuppressive effects in common carp.

Expression of P16 INK4a in testis of rhesus monkey during heat stress and testosterone undecanoate induced azoospermia or oligozoospermia☆

Previous studies on azoospermia or oligozoospermia induced by heat stress or high doses of testosterone mainly focused on germ cell apoptosis; no data regarding their possible effect on spermatogonia mitosis are available. We have established unilateral cryptorchid and testosterone undecanoate (TU)-treated monkey models and examined expression of P16 INK4a in the testis to look at its possible role in azoospermia or oligozoospermia induced by the heat stress or the TU treatment. The results showed that both heat stress and TU were capable of inducing expression of P16 INK4a mainly in spermatogonia and other types of germ cells as well as Sertoli cells at the later stage of germ cell apoptosis, namely on Day 10 after operation or on Day 60 after TU injection. It is, therefore, suggested for the first time that P16 INK4a protein may inhibit the spermatogonia mitosis in the testis at the later stage of the germ cell apoptosis, resulting in arrest of spermatogenesis.

Sertoli cell ectoplasmic specializations in the seminiferous epithelium of the testosterone-suppressed adult rat.

The Sertoli cell ectoplasmic specialization is a unique junctional structure involved in the interaction between elongating spermatids and Sertoli cells. We have previously shown that suppression of testicular testosterone in adult rats by low-dose testosterone and estradiol (TE) treatment causes the premature detachment of step 8 round spermatids from the Sertoli cell. Because these detaching round spermatids would normally associate with the Sertoli cell via the ectoplasmic specialization, we hypothesized that ectoplasmic specializations would be absent in the seminiferous epithelium of TE-treated rats, and the lack of this junction would cause round spermatids to detach. In this study, we investigated Sertoli cell ectoplasmic specializations in normal and TE-treated rat testis using electron microscopy and localization of known ectoplasmic specialization-associated proteins (espin, actin, and vinculin) by immunocytochemistry and confocal microscopy. In TE-treated rats where round spermatid detachment was occurring, ectoplasmic specializations of normal morphology were observed opposite the remaining step 8 spermatids in the epithelium and, importantly, in the adluminal Sertoli cell cytoplasm during and after round spermatid detachment. When higher doses of testosterone were administered to promote the reattachment of all step 8 round spermatids, newly elongating spermatids associated with ectoplasmic specialization proteins within 2 days. We concluded that the Sertoli cell ectoplasmic specialization structure is qualitatively normal in TE-treated rats, and thus the absence of this structure is unlikely to be the cause of round spermatid detachment. We suggest that defects in adhesion molecules between round spermatids and Sertoli cells are likely to be involved in the testosterone-dependent detachment of round spermatids from the seminiferous epithelium.

The Pattern of Inhibin/Activin - and B-Subunit Messenger Ribonucleic Acid Expression in Rat Testis after Selective Leydig Cell Destruction by Ethylene Dimethane Sulfonate

To further investigate the regulatory mechanisms responsible for the control of testicular inhibin/activin subunit gene expression, inhibin-α, -βA, and -βB messenger RNA (mRNA) levels were assessed after ethylene dimethane sulfonate (EDS)-induced destruction of Leydig cells (LC) in different animal models: the intact rat, the rat treated with high doses of testosterone, and the unilaterally cryptorchid rat. In intact rats, EDS selectively eliminates the mature adult-type LCs, activating the proliferation and differentiation of preexisting LC precursors into a new population of functionally active LCs. In this model, a single dose of EDS (75 mg/kg BW, ip) induced a significant increase in testicular inhibin-α and -βB mRNA levels 5 days after treatment (5.0- and 5.5-fold increases, respectively), whereas inhibin-βA mRNA remained undetectable upon Northern hybridization in control and EDS-treated testes. Moreover, in situ hybridization analysis demonstrated that the increased expression of inhibin-α and -βB mRNAs observed 5 days after EDS takes place mainly in Sertoli cells. Along with LC repopulation, the expression level of inhibin-α and -βB messages declined, and inhibin-α mRNA returned to control values on day 40 after EDS. This treatment, however, failed to alter the pattern of testicular expression of FSH receptor and androgen-binding protein mRNAs, thus suggesting selectivity for the above effects. In EDS-treated rats supplemented with high doses of testosterone, the preexisting mature LCs are destroyed, but, due to elevated testosterone concentrations, disruption of spermatogenesis is attenuated, and the post-EDS rise in serum gonadotropins is blocked; the latter prevents LC regeneration. In this model, a 5.0-fold increase in inhibin-α mRNA levels, similar to that found in intact animals, was detected 5 days after EDS administration, but the rise in inhibin-βB levels was partially delayed. In addition, the blockade of LC repopulation resulted in permanent elevation of inhibin-α and -βB messages throughout the study period. In unilaterally cryptorchid rats, the abdominal testis shows disrupted spermatogenesis and altered paracrine environment that expedites LC repopulation after EDS treatment. In this model, the abdominal testes showed a significant 2.5-fold increase in inhibin-α mRNA levels 5 days after EDS, but no effect was found in those of inhibin-βB. Further, the faster rate of LC repopulation resulted in precocious decline of inhibin-α mRNA levels. Finally, the expression of inhibin/activin subunit mRNAs was monitored during postnatal testicular development, specifically at the time of regression of fetal-type LCs and appearance of those of the adult type. High levels of expression of inhibin-α and -βB mRNAs were detected in neonatal and infantile testes. A sharp decline in both messages took place between days 15–20, i.e. at the time when fetal-type Leydig cells are replaced by adult-type cells. From this time point onward, inhibin-α and -βB mRNA levels remained low, ranging between 15–30% of the maximum. In conclusion, our results suggest that the adult-type LCs differentially modulate the expression of inhibin/activin subunit genes and point to a major inhibitory role in this cell type on expression of the inhibin-α gene.

The pattern of inhibin/activin alpha- and betaB-subunit messenger ribonucleic acid expression in rat testis after selective Leydig cell destruction by ethylene dimethane sulfonate.

To further investigate the regulatory mechanisms responsible for the control of testicular inhibin/activin subunit gene expression, inhibin-alpha, -betaA, and -betaB messenger RNA (mRNA) levels were assessed after ethylene dimethane sulfonate (EDS)-induced destruction of Leydig cells (LC) in different animal models: the intact rat, the rat treated with high doses of testosterone, and the unilaterally cryptorchid rat. In intact rats, EDS selectively eliminates the mature adult-type LCs, activating the proliferation and differentiation of preexisting LC precursors into a new population of functionally active LCs. In this model, a single dose of EDS (75 mg/kg BW, ip) induced a significant increase in testicular inhibin-alpha and -betaB mRNA levels 5 days after treatment (5.0- and 5.5-fold increases, respectively), whereas inhibin-betaA mRNA remained undetectable upon Northern hybridization in control and EDS-treated testes. Moreover, in situ hybridization analysis demonstrated that the increased expression of inhibin-alpha and -betaB mRNAs observed 5 days after EDS takes place mainly in Sertoli cells. Along with LC repopulation, the expression level of inhibin-alpha and -betaB messages declined, and inhibin-alpha mRNA returned to control values on day 40 after EDS. This treatment, however, failed to alter the pattern of testicular expression of FSH receptor and androgen-binding protein mRNAs, thus suggesting selectivity for the above effects. In EDS-treated rats supplemented with high doses of testosterone, the preexisting mature LCs are destroyed, but, due to elevated testosterone concentrations, disruption of spermatogenesis is attenuated, and the post-EDS rise in serum gonadotropins is blocked; the latter prevents LC regeneration. In this model, a 5.0-fold increase in inhibin-alpha mRNA levels, similar to that found in intact animals, was detected 5 days after EDS administration, but the rise in inhibin-betaB levels was partially delayed. In addition, the blockade of LC repopulation resulted in permanent elevation of inhibin-alpha and -betaB messages throughout the study period. In unilaterally cryptorchid rats, the abdominal testis shows disrupted spermatogenesis and altered paracrine environment that expedites LC repopulation after EDS treatment. In this model, the abdominal testes showed a significant 2.5-fold increase in inhibin-alpha mRNA levels 5 days after EDS, but no effect was found in those of inhibin-betaB. Further, the faster rate of LC repopulation resulted in precocious decline of inhibin-alpha mRNA levels. Finally, the expression of inhibin/activin subunit mRNAs was monitored during postnatal testicular development, specifically at the time of regression of fetal-type LCs and appearance of those of the adult type. High levels of expression of inhibin-alpha and -betaB mRNAs were detected in neonatal and infantile testes. A sharp decline in both messages took place between days 15-20, i.e. at the time when fetal-type Leydig cells are replaced by adult-type cells. From this time point onward, inhibin-alpha and -betaB mRNA levels remained low, ranging between 15-30% of the maximum. In conclusion, our results suggest that the adult-type LCs differentially modulate the expression of inhibin/activin subunit genes and point to a major inhibitory role in this cell type on expression of the inhibin-alpha gene.

Organizational effects of estrogens on brain vasotocin and sexual behavior in quail.

Reproductive behavior is sexually differentiated in quail: The male-typical copulatory behavior is never observed in females even after treatment with high doses of testosterone (T). This sex difference in behavioral responsiveness to T is organized during the embryonic period by the exposure of female embryo to estrogens. We showed recently that the sexually dimorphic medial preoptic nucleus (POM), a structure that plays a key role in the activation of male copulatory behavior, is innervated by a dense steroid-sensitive network of vasotocin-immunoreactive (VT-ir) fibers in male quail This innervation is almost completely absent in the female POM and is not induced by a chronic treatment with T, suggesting that this neurochemical difference could be organizational in nature. This idea was tested by injecting fertilized quail eggs of both sexes on day 9 of incubation with either estradiol benzoate (EB) (25 microg, a treatment that suppresses the capacity to show copulatory behavior in adulthood) or the aromatase inhibitor R76713 (10 microg, a treatment that makes adult females behaviorally responsive to T), or with the solvents as a control (C). At 3 weeks posthatch, all subjects were gonadectomized and later implanted with Silastic capsules filled with T. Two weeks later, all birds were perfused and brain sections were processed for VT immunocytochemistry. Despite the similarity of the adult endocrine conditions of the subjects (all were gonadectomized and treated with T Silastic implants providing the same plasma level of steroid to all subjects), major qualitative differences were observed in the density of VT-ir structures in the POM of the different groups. Dense immunoreactive structures (fibers and a few cells) were observed in the POM of C males but not females; EB males had completely lost this immunoreactivity (and lost the capacity to display copulatory behavior); and, conversely, R76713 females displayed a male-typical VT-ir system in the nucleus (and also high levels of copulatory behavior). Similar changes in immunoreactivity were seen in the nucleus of the stria terminalis and in the lateral septum (VT-ir fibers only in this case) but not in the magnocellular vasotocinergic system. These neurochemical changes closely parallel the effects of the embryonic treatments on male copulatory behavior. The vasotocinergic system of the POM can therefore be considered an accurate marker of the sexual differentiation of brain circuits mediating this behavior.

High doses of testosterone increase anticonflict behaviour in rat

Male rats exposed to high levels of testosterone for 8 weeks, or to one high dose of testosterone 24 h before testing, displayed an increase in punished responding in the Vogel conflict test. The findings may be taken as indirect support for the assumption that the conflict paradigm reflects not only anxiety but also impulsivity.

Imprinting of female offspring with testosterone results in insulin resistance and changes in body fat distribution at adult age in rats.

In women, a relative hyperandrogenicity is statistically associated with insulin resistance and centralization of body fat, which are predictors for the development of non-insulin-dependent diabetes mellitus. The aim of this study was to evaluate the effect of androgenization of newborn female rats on insulin sensitivity at adult age. To mimic the neonatal androgen peak normally observed in male rats, female pups were administered one high dose of testosterone (T) subcutaneously within 3 h after birth. They were then given back to their mothers and followed to adult age. At the end of the week 9, tail samples were taken, showing no differences in fasting plasma concentrations of glucose, lactate, insulin, or free fatty acids between T-treated rats and controls. Plasma concentrations of T and progesterone were significantly lower in the T-treated rats, whereas no differences were found in the levels of corticosterone, estradiol, insulin-like growth factor I, or ACTH. After 10 wk, insulin sensitivity was studied with hyperglycemic and euglycemic hyperinsulinemic (5 mU insulin/kg/min) clamp techniques. The T-treated rats showed insulin resistance with both techniques, which was overcome with time and increasing insulin concentrations during the clamp measurements. The T-treated rats were also heavier and had increased relative weights of skeletal muscles and the spleen. Parametrial, retroperitoneal, and inguinal adipose tissues decreased in weight while mesenteric adipose tissue tended to increase, resulting in an approximately 30-50% larger mesenteric than other adipose tissues. It is concluded that neonatal T imprinting of female rats is followed by insulin resistance, changes in adipose tissue distribution, and an enlarged lean mass, without elevation of circulating T. Similar changes are seen in adult female rats or women receiving T.

Reduced extracellular levels of serotonin in the amygdala of androgenized female rats

The object of this study was to evaluate the effect of androgenization on the extracellular concentrations of serotonin in the amygdala of otherwise intact female rats. One group of animals received one high dose of testosterone (1 mg, s.c.) within three hours after birth, one group received continuous administration of testosterone by means of silicone tubings (50 mm) for approximately 20 days starting at day 40, and one group received testosterone both in the neonatal period and from day 40 and onwards. Assessment of extracellular levels of serotonin in the amygdala was undertaken around day 60 using in vivo microdialysis with HPLC detection; the animals were awake and unrestrained during the microdialysis procedure. Dialysate serotonin concentrations did not differ between the three groups of androgenized animals; however, in all three groups, dialysate levels of serotonin were significantly lower than in controls receiving sesame oil neonatally and empty tubings at day 40. It is suggested that the effects of testosterone on sex-dependent behaviours such as aggression and sexual activity may be at least partly due to a reduction in brain serotonin function.

Molecular Mechanisms of Reappearance of Luteinizing Hormone Receptor Expression and Function in Rat Testis after Selective Leydig Cell Destruction by Ethylene Dimethane Sulfonate

Considering the major role of LH in the control of Leydig cell (LC) development and function, we aimed to characterize further the pattern of LH receptor (LHR) expression in two experimental paradigms: the rat treated with ethylene dimethane sulfonate (EDS), in which the selective destruction of preexisting mature LCs induces the proliferation and differentiation of newly formed LCs, a process that takes place in the presence of high levels of gonadotropins; and the EDS-rat treated with a high dose of testosterone (EDS + T), in which the LH secretion is suppressed, and consequently LC development after EDS arrested. In EDS rats, serum T was suppressed and testicular LHR binding became undetectable on days 5 and 15 after treatment. The pattern of LHR messenger RNA (mRNA) expression was profoundly modified: only one of the splice variants [1.8-kilobase (kb)] persisted, whereas the others disappeared. On days 20 and 45 after EDS, along with LC repopulation, serum T and LHR binding recovered, and the pattern of LHR mRNA expression gradually returned to that resembling controls. In EDS + T rats, a similar drop in testicular LHR binding and change in the pattern of LHR mRNA expression was detected on days 5 and 15 after treatment. However, on days 20 and 45, no recovery either in LHR binding or in expression of the longer LHR mRNA splice variants was observed, showing that LH is needed to induce LHR expression in repopulating LCs, at least to a quantitatively significant level. To gain further insight into the mechanism(s) by which LH acts on LC precursors, the translational status of the 1.8-kb LHR transcript, persistently expressed after EDS, was analyzed and compared with that of the 6.8-kb message. In polysome distribution analysis of total testicular RNA, the 6.8-kb LHR message was highly associated with polysomes, whereas the 1.8-kb variant was mainly localized to prepolysomal fractions, both in control and EDS testes, thus predicting lower translational efficiency. In addition, considering that only LCs express LHRs in the testis, the time course of the reappearance of functional receptors was mapped by evaluating testicular responsiveness to human recombinant LH in vitro. No response to LH stimulation was detected 5 days after EDS. However, cAMP response to LH was observed on days 15 and 20, regardless of the presence of high (EDS) or suppressed (EDS + T) LH in the donor animal. Hence, the appearance of functional LHRs, qualitatively, can take place in the absence of measurable LH levels. In EDS-treated rats, the appearance of the cAMP response coincided with those of pregnenolone, progesterone, and T. In contrast, no LH-induced steroid release was observed in EDS + T rats, indicating that steroidogenic response in developing LC requires LH priming. In conclusion, the appearance of functional LHRs, at a low level of expression, in LC precursors is an LH-independent developmental event, essential for the subsequent LH-dependent maturational steps, including the onset of steroidogenesis and increased LHR expression. In addition, our results cast doubt on a major functional role of the truncated (1.8-kb) form of LHR mRNA, which persists after EDS at a high level of expression, in the early Leydig cell precursors.

Molecular mechanisms of reappearance of luteinizing hormone receptor expression and function in rat testis after selective Leydig cell destruction by ethylene dimethane sulfonate.

Considering the major role of LH in the control of Leydig cell (LC) development and function, we aimed to characterize further the pattern of LH receptor (LHR) expression in two experimental paradigms: the rat treated with ethylene dimethane sulfonate (EDS), in which the selective destruction of preexisting mature LCs induces the proliferation and differentiation of newly formed LCs, a process that takes place in the presence of high levels of gonadotropins; and the EDS-rat treated with a high dose of testosterone (EDS + T), in which the LH secretion is suppressed, and consequently LC development after EDS arrested. In EDS rats, serum T was suppressed and testicular LHR binding became undetectable on days 5 and 15 after treatment. The pattern of LHR messenger RNA (mRNA) expression was profoundly modified: only one of the splice variants [1.8-kilobase (kb)] persisted, whereas the others disappeared. On days 20 and 45 after EDS, along with LC repopulation, serum T and LHR binding recovered, and the pattern of LHR mRNA expression gradually returned to that resembling controls. In EDS + T rats, a similar drop in testicular LHR binding and change in the pattern of LHR mRNA expression was detected on days 5 and 15 after treatment. However, on days 20 and 45, no recovery either in LHR binding or in expression of the longer LHR mRNA splice variants was observed, showing that LH is needed to induce LHR expression in repopulating LCs, at least to a quantitatively significant level. To gain further insight into the mechanism(s) by which LH acts on LC precursors, the translational status of the 1.8-kb LHR transcript, persistently expressed after EDS, was analyzed and compared with that of the 6.8-kb message. In polysome distribution analysis of total testicular RNA, the 6.8-kb LHR message was highly associated with polysomes, whereas the 1.8-kb variant was mainly localized to prepolysomal fractions, both in control and EDS testes, thus predicting lower translational efficiency. In addition, considering that only LCs express LHRs in the testis, the time course of the reappearance of functional receptors was mapped by evaluating testicular responsiveness to human recombinant LH in vitro. No response to LH stimulation was detected 5 days after EDS. However, cAMP response to LH was observed on days 15 and 20, regardless of the presence of high (EDS) or suppressed (EDS + T) LH in the donor animal. Hence, the appearance of functional LHRs, qualitatively, can take place in the absence of measurable LH levels. In EDS-treated rats, the appearance of the cAMP response coincided with those of pregnenolone, progesterone, and T. In contrast, no LH-induced steroid release was observed in EDS + T rats, indicating that steroidogenic response in developing LC requires LH priming. In conclusion, the appearance of functional LHRs, at a low level of expression, in LC precursors is an LH-independent developmental event, essential for the subsequent LH-dependent maturational steps, including the onset of steroidogenesis and increased LHR expression. In addition, our results cast doubt on a major functional role of the truncated (1.8-kb) form of LHR mRNA, which persists after EDS at a high level of expression, in the early Leydig cell precursors.