Testicular Interstitial Fluid Testosterone Research Articles

Male reproductive toxicity of CrVI: In-utero exposure to CrVI at the critical window of testis differentiation represses the expression of Sertoli cell tight junction proteins and hormone receptors in adult F1 progeny rats

The effect of gestational exposure to CrVI (occupational/environmental pollutant and target to Sertoli cells(SC)) was tested in a rat model during the testicular differentiation from the bipotential gonad may interrupt spermatogenesis by disrupting SC tight junctions(TJ) and it’s proteins and hormone receptors. Pregnant Wistar rats were exposed to 50/100/200ppm CrVI through drinking water during embryonic days 9–14. On Postnatal day 120, testes were subjected to ion exchange chromatographic analysis and revealed increased level of CrIII in SCs and germ cells, serum and testicular interstitial fluid(TIF). Microscopic analyses showed seminiferous tubules atrophy and disruption of SC TJ, which also recorded decreased testosterone in TIF. mRNA and Protein expression analyses attested decreased level of Fshr, Ar, occludin and claudin-11 in SCs. Immunofluorescent detection revealed weak signal of TJ proteins. Taken together, we concluded that gestational exposure to CrVI interferes with the expression of SC TJ proteins due to attenuated expression of hormone receptors.

Influence of streptozotocin-induced diabetes and insulin treatment on the pituitary-testicular axis during sexual maturation in rats.

Effects of streptozotocin (STZ)-diabetes and insulin treatment on the functioning of pituitary-testicular axis during sexual maturation was studied. Prepubertal (30 days old) and pubertal (50 days old) male Wistar rats were made diabetic by a single injection of STZ. A group of diabetic rats was given insulin (3U/100 g b.wt./day in 2 equally divided doses), 3 days after STZ treatment. Prepubertal and pubertal rats of all groups were killed on postnatal days 51 and 71, respectively. STZ-diabetes caused marked reduction in serum LH, FSH, prolactin, testosterone and testicular interstitial fluid testosterone as well as the activities of Leydig cellular steroidogenic enzymes (3beta-and 17beta-hydroxysteroid dehydrogenases). Insulin treatment to diabetic rats maintained these changes at control range except FSH and prolactin in prepubertal rats. The results indicate that (i) diabetes-induced steroidogenic lesions in Leydig cells represent a direct consequence of dysfunctioning of pituitary-testicular axis, (ii) the adverse effects of diabetes on pituitary-testicular functions are influenced by age of its induction and (iii) optimum insulin level is essential for the acquisition of Leydig cellular steroidogenic efficacy during sexual development.

Combined administration of low-dose gossypol acetic acid with desogestrel/mini-dose ethinylestradiol/testosterone undecanoate as an oral contraceptive for men

To evaluate the efficacy and feasibility of a new regimen of low-dose gossypol acetic acid (GA) combined with desogestrel/ethinylestradiol and testosterone undecanoate (DSG/E/TU) as a male contraceptive, adult male rats were fed orally with GA (12.5 mg/kg/day) and DSG (0.125 mg/kg)/E (0.025 mg/kg)/TU (100 mg/kg) daily for 8 weeks as loading dose until infertility, and a similar low dose of GA alone for infertility maintenance. Control animals were administered a single low dose of GA (12.5 mg/kg/day) or DSG (0.125 mg/kg)/E (0.025 mg/kg)/TU (100 mg/kg), and vehicle, respectively. Results demonstrated that the combined dosage regimen could damage epididymal sperm motility and density, and induce infertility within 8 weeks in rats; the infertility could be consistently sustained by giving single GA (12.5 mg/kg/day), and was reversible in about 8 weeks following withdrawal of gossypol. The regimen rendered treated male rats with spermiation failure within a period of 6–20 weeks of treatment. Also, the serum luteinizing hormone, follicle-stimulating hormone and testicular interstitial fluid testosterone levels showed a transient decrease at the end of 6 or 8 weeks, which returned to control levels after 8 weeks of recovery phase. No hypokalemia or other adverse effects in viscera were observed. These results provide a promising approach to using the new regimen for the development of an effective and reversible oral male contraceptive.

Continuously proliferative stem germ cells partially repopulate the aged, atrophic rat testis after gonadotropin-releasing hormone agonist therapy.

Aging in the male human is accompanied by testicular atrophy, although relatively little is known about the mechanisms underlying germ cell loss. Testicular atrophy in the aged Brown Norway rat, an animal model for studies of aging in the human, has been attributed to a loss of spermatogonial stem cells. However, examination of testicular cross-sections from 27-mo-old Brown Norway rats indicated that approximately 14% of type A spermatogonia were stem cells. Furthermore, using bromodeoxyuridine labeling, we found that approximately 47% of these stem cells were actively dividing, with a cell cycle time of approximately 12.6 days. Both serum and testicular interstitial fluid testosterone levels were depressed in the aged rat. Therapy with the GnRH agonist, leuprolide, which has been empirically shown to reverse testicular atrophy in other models of germ cell loss, also partially restored spermatogenesis in the aged Brown Norway rat. The extent of testicular atrophy varied considerably, not only within the control and leuprolide-treatment groups but also between the left and right testes of the same animals. No significant difference was found between the mean percentage of populated tubules in 31-mo-old control animals (16.2 +/- 28%, mean +/- SD) and 31-mo-old leuprolide-treated animals (20.9 +/- 19.8%), but categorical comparisons showed that significantly fewer leuprolide-treated animals and testes contained < or = 1% populated tubules, indicating that GnRH agonist therapy stimulates differentiation of type A spermatogonia. An increase in the ratio of soluble to membrane stem cell factor mRNA levels was present in aged rats and partially reversed following leuprolide therapy.

IMPACT OF NEONATAL HYPOTHYROIDISM ON LEYDIG CELL NUMBER, PLASMA, AND TESTICULAR INTERSTITIAL FLUID SEX STEROIDS CONCENTRATION

We have previously demonstrated that neonatal and transient neonatal hypothyroidism modulates Leydig, Sertoli, and germ cell numbers, sex steroids and androgen binding protein concentration. The present study was undertaken to study the effect of neonatal onset hypothyroidism on Leydig and peritubular myoid cell numbers, plasma and testicular interstitial fluid (TIF) sex steroid concentration at different age groups of Wistar rats. Hypothyroidism was induced by giving 0.05% methimazole (MMI) to lactating mothers or directly to the male pups from day 1 postpartum through days 10, 15, 30, 40 and 60 postpartum. To confirm hypothyroidism, plasma thyroid hormones and TSH were assayed. Plasma and TIF testosterone, progesterone, dihydrotestosterone (DHT) and estradiol were assayed by radioimmunoassay. Leydig cell number in hypothyroid rats were less than the age-matched controls. The diameter of Leydig cells in hypothyroid rats was smaller than the controls but 10 days old hypothyroids alone had larger than control rats. A significant decrease of peritubular myoid cell number was observed in 30, 40 and 60 days hypothyroid rats and increased in 10 and 15 days hypothyroidism. Hypothyroid rats had elevated level of plasma LH and decreased GH (except day 10 postpartum). Plasma PRL level was increased in 10 and 15 days hypothyroid rats and an opposite effect was observed in 40 and 60 days hypothyroidism. Plasma testosterone, DHT and estradiol were decreased in all hypothyroid rats. However, plasma progesterone level in hypothyroid rats was significantly higher at days 10, 30, and 40 postpartum and an opposite effect was seen in 15 and 60 days experimental groups. TIF testosterone and progesterone titre showed a consistent decrease in hypothyroid rats irrespective of the duration. In hypothyroid rats, TIF DHT levels decreased significantly in days 10, 40 and 60 postpartum. However, it increased in days 15 and 30 postpartum. Except at day 10 postpartum, the level of TIF estradiol in hypothyroid rats was significantly less than their age matched controls. Our data clearly indicate that neonatal onset hypothyroidism adversely affect Leydig cell proliferation along with impaired steroidogenesis.

Chronic corticosterone treatment impairs Leydig cell 11beta-hydroxysteroid dehydrogenase activity and LH-stimulated testosterone production.

The effects of excess corticosterone on luteinizing hormone (LH)-stimulated Leydig cell testosterone production and activity of 11beta-HSD was studied. Adult male rats (200-250 g body weight) were treated with corticosterone-21-acetate (2 mg/100 g body weight, i.m., twice daily) for 15 days. Another set of rats was treated with corticosterone (dose as above) plus LH (ovine LH 100 microg/kg body weight, s.c., daily) for 15 days. Corticosterone administration significantly increased serum and testicular interstitial fluid (TIF) corticosterone but decreased testosterone levels. Administration of LH with corticosterone partially prevented the decrease in serum and TIF testosterone. The oxidative activity of 11beta-hydroxysteroid dehydrogenase (11beta-HSD) was significantly decreased in Leydig cells of rats treated with corticosterone alone and in combination with LH. The direct effect of corticosterone on Leydig cell steroidogenic potency was also studied in vitro. Addition of corticosterone to Leydig cell culture showed a dose dependent effect on LH-stimulated testosterone production. Corticosterone at 50 and 100 ng/ml did not alter LH-stimulated testosterone production, but at high doses (200-400 ng/ml), decreased basal and LH-stimulated testosterone production. Basal and LH-stimulated cAMP production was not altered by corticosterone in vitro. It is concluded from the present study that elevated levels of corticosterone decreased the oxidative activity of 11beta-HSD and thus resulting in impaired Leydig cell steroidogenesis and the inhibitory effects of corticosterone on testosterone production appear to be mediated through inhibition of LH signal transduction at post-cAMP level.

Chronic administration of corticosterone impairs LH signal transduction and steroidogenesis in rat Leydig cells

The mechanism involved in the inhibitory actions of chronic corticosterone treatment on Leydig cell steroidogenesis was studied in adult Wistar rats. Rats were treated with corticosterone-21-acetate (2 mg/100 g body weight, i.m., twice daily) for 15 days and another set of rats was treated with corticosterone plus ovine luteinizing hormone (oLH) (100 μg/kg body weight, s.c., daily) for 15 days. Chronic treatment with corticosterone increased serum corticosterone but decreased serum LH, testosterone, estradiol and testicular interstitial fluid (TIF) testosterone and estradiol concentrations. Administration of LH with corticosterone partially prevented the decrease in serum and TIF testosterone and estradiol. Leydig cell LH receptor number, basal and LH-stimulated cAMP production were diminished by corticosterone treatment which remained at control level in the corticosterone plus LH treated rats. Activities of steroidogenic enzymes, 3β- and 17β-hydroxysteroid dehydrogenase (3β-HSD and 17β-HSD) were significantly decreased in corticosterone treated rats. LH plus corticosterone treatment did not affect 3β-HSD activity but decreased 17β-HSD activity, indicating a direct inhibitory effect of excess corticosterone on Leydig cell testosterone synthesis. The indirect effect of corticosterone, thus, assume to be mediated through lower LH which regulates the activity of 3β-HSD. Basal, LH and cAMP-stimulated testosterone production by Leydig cells of corticosterone and corticosterone plus LH treated rats were decreased compared to control suggesting the deleterious effect of excess corticosterone on LH signal transduction and thus steroidogenesis.

Transient Neonatal Hypothyroidism Alters Plasma and Testicular Sex Steroid Concentration in Puberal Rats

The stimulatory and inhibitory effects on testicular steroidogenesis of transient neonatal hypothyroidism from day 1 postpartum through different postnatal developmental events on testis at puberal age (60 days old) were studied in vivo. Hypothyroidism was induced in neonates by feeding the lactating mother or directly with 0.05% methimazole (MMI) through drinking water from the day of parturition to 10, 15, 30, 40 and 60 days, and were killed at day 60 postpartum. Plasma and testicular interstitial fluid (TIF) progesterone, testosterone, dihydrotestosterone (DHT) and estradiol concentrations were assessed. Testis weight and volume significantly increased in rats subjected to 10 and 15 days of hypothyroidism, decreased in rats subjected to 30, 40 and 60 days of hypothyroidism. A consistent increase in Leydig cell number was seen in puberal rats subjected to transient neonatal hypothyroidism but decreased in 60 days hypothyroid rats. Peritubular myoid cell number was consistently decreased in all experimental rats. Leydig cell diameter decreased consistently in all experimental groups. Persistent hypothyroidism (60 days hypothyroid) consistently decreased both plasma and TIF sex steroids. In transient hypothyroid rats, progesterone concentration decreased in both plasma and TIF. Transient hypothyroidism from birth to day 10 postnatal age maintained normal titre of plasma testosterone, whereas a significant increase in TIF testosterone concentration was evident when compared with controls. All other groups of rats subjected to transient neonatal hypothyroidism had consistently low titres of plasma and TIF testosterone. Plasma DHT concentrations in rats subjected to transient neonatal hypothyroidism remained unaltered. However, TIF DHT increased in 10 days hypothyroids, decreased in 30 and 40 days hypothyroid rats and remained unaltered in 15 days hypothyroids. Transient hypothyroidism registered normal titres of plasma estradiol in all groups except in 30 days hypothyroids, which registered an increase, while a consistent increase in TIF estradiol concentration was observed. The present study indicates that transient neonatal hypothyroidism, when restricted up to 10 days of postnatal life, at puberal age Stimulates testosterone, DHT and estradiol secretion and when extended beyond 10 days of postnatal life shifts towards estradiol secretion.

Interactions Between Alcohol‐ and Opioid‐Induced Suppression of Rat Testicular Steroidogenesis In Vivo

To examine interactions between alcohol and endogenous opioids in their suppressive effects on rat testicular function, the opioid antagonist naltrexone or the opioid agonist morphine was administered to adult male rats alone or in combination with alcohol. Serum testosterone, testicular interstitial fluid (TIF) testosterone, and TIF volumes were measured to assess testicular function. Naltrexone induced dose-dependent increases in serum and TIF testosterone levels without changes in TIF volume. Alcohol (0.5 g/kg) inhibited naltrexone-induced stimulation of testosterone secretion and shifted the naltrexone dose-response curve to the right. Conversely, naltrexone (0.05 mg/kg) inhibited alcohol-induced suppression of testosterone secretion and shifted the alcohol dose-response curve to the right. Relatively high doses of naltrexone (5 to 30 mg/kg) were needed to stimulate testosterone secretion maximally in rats treated with a low dose of alcohol (0.5 g/kg) and to stimulate normal levels of testosterone secretion in rats treated with a high dose of alcohol (2 g/kg). In addition, combined treatment with 1 and 30 mg/kg of naltrexone and 0.5 to 2 g/kg of alcohol did not alter blood alcohol concentrations significantly, suggesting that the interactions between alcohol and naltrexone were unrelated to gross changes in alcohol metabolism or bioavailability factors. Simultaneous treatments with a low dose of alcohol (0.3 g/kg), near the threshold of efficacy, and low-moderate doses of morphine (0.3 to 3 mg/kg) were not additive in suppressing testosterone secretion, compared with either agent alone. These results support the hypothesis that opioid antagonists can reverse the suppressive effect of alcohol on testicular steroidogenesis, but the results also suggest that endogenous opioids do not exclusively mediate alcohol's effects on testosterone secretion.

The effects of a gonadotropin-releasing hormone antagonist on androgen-binding protein distribution and other parameters in the adult male rat.

The effects of gonadotropins and gonadal steroids on androgen-binding protein (ABP) production and its distribution among the epididymis, seminiferous tubule fluid (STF), testicular interstitial fluid (TIF), and blood were studied in 300-g adult male Sprague-Dawley rats. The rats either received no treatment or their pituitary function was suppressed by administration of the GnRH antagonist [AcD2Nal,D4ClDPhe2,D3Pal3,Arg5,DGlu6 (AA),D-Ala10]LHRH (antagonist). Other groups of rats were treated with hCG, FSH, FSH plus hCG, testosterone, or estradiol, alone or together with antagonist. Treatment was conducted for 30 days, after which time, ABP was detected by its ability to bind [3H]5 alpha-dihydrotestosterone. Transport of ABP from the testis to the epididymis was inhibited by antagonist administration. Simultaneous treatment with antagonist and hCG, or antagonist and hCG plus FSH prevented antagonist-induced inhibition of ABP transport. Neither FSH, testosterone, nor estradiol alone was effective in this process. Inhibition of ABP transport to the epididymis was accompanied by its accumulation within the testis. Treatment with antagonist and FSH resulted in a 4.5-fold increase in the concentration of ABP in TIF, but had little effect on the amount of ABP in STF, indicating selective secretion of ABP from the basal surface of the Sertoli cells. Treatment with antagonist alone, antagonist together with testosterone or estradiol, or estradiol alone resulted in increased concentrations of ABP in both TIF and STF, but the increase in TIF was proportionately greater. Treatment with hCG or FSH plus hCG alone or with antagonist not only facilitated ABP transport to the epididymis, but also increased TIF levels of ABP above control values. The former treatment resulted in increased concentrations of testosterone in TIF, but not in STF. Both treatments resulted in testosterone levels in both compartments that were higher than those in animals treated with antagonist alone. No treatment had a statistically significant effect on blood levels of ABP. About 50% of ABP synthesis appears to be constitutive, i.e. is not regulated by hormones. Although ABP production continues in the presence of antagonist, its transport to the epididymis is halted, indicating that epididymal transport of ABP is a hormone-dependent process. It is likely that elevated intratesticular levels of testosterone or FSH and testosterone acting in concert regulate epididymal transport of ABP.

Effects of Ammonium Perfluorooctanoate on Leydig-Cell Function: In Vitro, in Vivo, and ex Vivo Studies

Ammonium perfluorooctanoate (C8) produced a dose-dependent increase in Leydig cell adenomas in Crl:CD BR (CD) rats fed 0, 30, or 300 ppm for 2 years. Administration of C8 to adult male CD rats, by gavage for 14 days, produced decreased serum and testicular interstitial fluid testosterone levels and increased serum estradiol levels. The C8-mediated decrease in the serum testosterone levels appeared to be due to a lesion at the level of the testis. These endocrine changes may play a role in the C8 induction of Leydig cell tumors. In the present work, C8 was examined for its ability to (1) directly affect Leydig cells in vitro using isolated Leydig cells from untreated rats and ex vivo using Leydig cells isolated from C8-treated rats, (2) affect testicular interstitial fluid hormone levels, and (3) induce aromatase activity. These studies were conducted to investigate the hypothesis that C8 produces an increase in estradiol by inducing cytochrome P450 XIX (aromatase), which converts testosterone to estradiol, and that the elevated estradiol levels ultimately produce Leydig cell hyperplasia and adenoma formation by acting as a mitogen or enhancing growth factor secretion. In the in vivo and ex vivo studies, adult male CD rats were gavaged with either 0 or 25 mg/kg/day C8 for 14 days. In addition to the ad libitum control, a second control group was pair-fed to the 25 mg/kg/day C8 group. In the in vitro and ex vivo studies, Leydig cells were isolated from testes of adult males by collagenase digestion followed by enrichment over Percoll gradients. A dose-dependent decrease in testosterone levels was observed in hCG-stimulated Leydig cells treated in vitro with C8 for 5 hr (IC50 approximately 200 μM). In contrast, ex vivo studies demonstrated an increase in testosterone production in hCG-stimulated Leydig cells from C8-treated rats when compared to Leydig cells isolated from either the ad libitum or pair-fed control rats. The in vitro data demonstrate that C8 directly inhibits testosterone release from Leydig cells, while the ex vivo data demonstrate that this inhibition is reversible. In the in vivo study, serum and testicular interstitial fluid estradiol concentrations were significantly higher in the C8-treated rats when compared to the pair-fed control group. In addition, testicular interstitial fluid transforming growth factor α (TGF α) levels were also increased, consistent with the hypothesis that estradiol may modulate growth factor expression within the testis. In a follow-up in vivo study, C8 produced a 4.5-fold increase in hepatic aromatase when compared to the pair-fed control, but did not increase aromatase activity in the testis, muscle, or fat. Collectively, these data suggest that the increase in serum estradiol levels from C8-treated rats is primarily due to aromatase induction in the liver.

Restoration of Spermatogenesis and Subsequent Fertility by Direct Intratesticular Hormonal Therapy

Testosterone-laden microspheres (TLM) were used in an attempt to restore spermatogenesis and sustain fertility in rats with previously suppressed gonadal function. Adult rats received 62.5μg. gonadotropin-releasing hormone antagonist (GnRH-antagonist) per day for 15 days prior to being divided into three groups: 1) animals to be examined immediately, 2) animals to continue receiving 62.5μg. GnRH-antagonist per day alone, and 3) animals to continue receiving GnRH-antagonist + a single intratesticular injection of 20mg. TLM per testis. Unoperated control and sham-operated animals were also studied. Testicular interstitial fluid (TIF) testosterone concentrations, testicular sperm production and fertility were assessed 105 days after initiation of the experiment. Testicular interstitial fluid testosterone concentrations and sperm production were significantly reduced from control values after the initial 15-day GnRH-antagonist treatment (p < .05). After 105 days of GnRH-antagonist treatment, these values were further reduced (p < .05), but the TIF testosterone and sperm production values of GnRH-antagonist treated animals receiving TLM supplementation were not different from those of controls (p < .05). Fertility trials were also performed. Animals which had received GnRH-antagonist alone for 90 days were completely infertile, but animals receiving GnRH-antagonist + TLM for 90 days had fertility values not different from those of control animals (p < .05). Thus, spermatogenesis reduced because of testicular insufficiency was restored to normal, as was fertility, by intratesticular administration of TLM. This technique has possible clinical applications in selected groups of infertile men.

Reduced testosterone during puberty results in a midspermiogenic lesion.

The aim of this study was to determine the role of testosterone, as reflected in the testicular interstitial fluid, in the completion of the first wave of spermatogenesis and to further elucidate its role in spermiogenesis. At weekly intervals beginning with 26-day-old rats, body and testis weights were obtained, testicular interstitial fluid testosterone (TIF-T) was assayed, daily sperm production (DSP) was determined, and testicular tissue was structurally analyzed by light and electron microscopy. At 40 days postpartum, half the rats were treated with ethane dimethanesulphonate (EDS) to temporarily reduce Leydig cells. The other half served as controls and were treated with the vehicle. The timing of EDS treatment was just prior to the elongation of spermatids. At Day 47 (1 week after EDS treatment), TIF-T, testis weight, DSP, and number of Leydig cells were significantly reduced. At Day 54 (2 weeks after treatment), TIF-T had returned to the normal adult level, Leydig cell repopulation was apparent, and testis weight was normal. The DSP returned to normal by Day 61 (3 weeks after treatment). At 1 and 2 weeks after treatment, Step 8-9 spermatids were partially or completely detached from Sertoli cells. Results indicate that a temporary reduction of testosterone during the peripubertal period leads to a temporary reduction of the DSP approximately 1 week later. It is suggested that reduced testosterone is associated with a mid-spermiogenic lesion interfering with stable attachment of Step 8-9 spermatids to Sertoli cells during Stage VIII-IX of the spermatogenic cycle.

Termination of the peripubertal FSH increase in male rats.

To determine if the pubertal testosterone rise plays a role in the termination of the peripubertal follicle-stimulating hormone (FSH) increase, male rats were injected with ethylene dimethanesulfonate (EDS) at 40 days of age to eradicate the Leydig cells just before the onset of the testosterone rise. Rats were decapitated at weekly intervals from age 26 to 96 days. Compared with vehicle-injected controls, EDS treatment resulted in a delay in the peripubertal increase in the relative weights of prostates and seminal vesicles of approximately 2 wk. Serum testosterone remained at pretreatment levels for 1 wk postinjection. Testicular interstitial fluid testosterone remained at pretreatment concentrations for considerably longer and was significantly lower than controls for 2 wk postinjection. EDS treatment resulted in serum FSH levels that were elevated by 1 wk postinjection. They remained significantly higher than controls until 96 days of age. Compared with controls, serum alpha-inhibin was elevated after EDS as was serum luteinizing hormone. These results suggest that the pubertal testosterone increase plays an important role in terminating the peripubertal FSH rise.

Nitric oxide control of steroidogenesis: Endocrine effects of N G-nitro-L-arginine and comparisons to alcohol

Recent studies suggest that nitric oxide (NO) may regulate hormone biosynthesis and secretion. This was tested by treating male rats with N G-nitro-L-arginine methyl ester (NAME), a NO synthase inhibitor, and measuring serum and testicular interstitial fluid testosterone and serum corticosterone, luteinizing hormone (LH), and prolactin (PRL). The effect of N G-nitro-L-arginine (NA), a less-soluble form of the same NO synthase inhibitor, on the reproductive suppressant actions of alcohol was also examined. NAME increased testosterone and corticosterone secretion dose-dependently without affecting LH and PRL secretion. The alcohol-induced suppression of testosterone or LH secretion was not altered by treatment with NA. Although effects of NAME and NA on other systems may be involved, these results indicate that testicular and adrenal steroidogenesis are negatively regulated by endogenos NO and that NO does not regulate LH and PRL secretion or inhibit the testicular steroidogenic pathway in the same way as alcohol.

Effects of Alcohol on β‐Endorphin and Reproductive Hormones in the Male Rat

In an attempt to examine the relationship between alcohol-induced alterations in immunoreactive beta-endorphin (i-beta E) levels in the hypothalamic-pituitary-gonadal axis and the synthesis and release of reproductive hormones, male rats were treated with either an acute intraperitoneal injection of alcohol or were chronically exposed to an alcohol-containing liquid diet. Hypothalamic, pituitary, serum, and testicular levels of immunoreactive beta-endorphin (i-beta E) and serum levels of luteinizing hormone (LH) and testosterone were measured at various times after initiation of these treatments. Testicular interstitial fluid (TIF) volumes and levels of TIF i-beta E and testosterone were also measured 4 hr after acute treatment as an index of testicular release of these substances. Acute alcohol decreased pituitary levels of i-beta E and increased serum levels of the peptide for up to 1 hr after its injection, but did not alter hypothalamic or testicular levels. Acute alcohol markedly increased TIF i-beta E and decreased TIF testosterone and TIF volume. Sharp decreases in serum LH and testosterone were observed in association with these acute changes in i-beta E levels in the pituitary, blood, and testes. During chronic alcohol exposure serum testosterone levels were substantially depressed, but tolerance appeared to develop quickly to the chronic effects of alcohol on serum LH. Similarly, tolerance to alcohol's effects on i-beta E levels in the pituitary and serum also appeared to develop during chronic alcohol administration. However, hypothalamic and testicular i-beta E levels were markedly suppressed by chronic alcohol administration in contrast to the lack of effect observed after acute alcohol administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamics of testosterone secretion by the rat testis: implications for measurement of the intratesticular levels of testosterone.

Testosterone concentrations have been measured in testicular interstitial fluid (IF), and in blood plasma sampled from various parts of the rat testis and spermatic cord, to assess (1) the most accurate method for determination of the intratesticular levels of testosterone, and (2) the route of secretion of testosterone from the testis. In untreated adult rats, testosterone concentrations were highest in blood collected from veins on the surface of the testis (269.50 +/- 30.63 (S.E.M.) nmol/l), but were reduced by 56% on average in blood collected from veins at the proximal end of the spermatic cord (123.06 +/- 24.75 nmol/l), and were reduced considerably in peripheral venous blood (4.55 +/- 0.55 nmol/l). Similar changes occurred in adult rats in which steroidogenesis was either stimulated (by treatment with human chorionic gonadotrophin; hCG) or inhibited (by treatment with aminoglutethimide; AMG), and in rats of various ages during sexual maturation. The reduction in testosterone levels during passage of blood from the testis up the spermatic cord is probably due mainly to dilution by incoming arterial blood which transfers to venous blood via anastomoses in the spermatic cord. Venous-arterial transfer of testosterone in the cord contributed to this in only a minor way. Concentrations of testosterone in testicular IF were always greater than testicular venous concentrations in control, developing and hCG-stimulated rats, but were comparable in rats treated with AMG to suppress Leydig cell steroidogenesis. These and other results demonstrate that the method of drip-collection of IF results in over-estimation of the actual intratesticular levels of testosterone.(ABSTRACT TRUNCATED AT 250 WORDS)

Increase in Leydig cell responsiveness in the unilaterally cryptorchid rat testis and its relationship to the intratesticular levels of testosterone.

Adult rats were made unilaterally cryptorchid (UCD) and 6-7 weeks later Leydig cells were isolated from the scrotal and abdominal testes and their capacity to secrete testosterone in vitro was compared. Basal testosterone production by Leydig cells from the abdominal testes of UCD rats was lowered, compared with cells from the contralateral scrotal testes, whilst their responsiveness to both human chorionic gonadotrophin and an LH releasing hormone agonist was enhanced two- to threefold (P less than 0.001) compared both with cells from the contralateral scrotal testes and with cells isolated from untreated rats of the same age. In the UCD rats, concentrations of testosterone in testicular interstitial fluid (IF) were reduced (P less than 0.001) by 70-90% in abdominal, compared with scrotal, testes. A similar reduction was evident in the levels of testosterone in spermatic venous blood, and both this decrease and that in IF levels of testosterone varied according to the degree of testicular involution. The ontogeny of the above changes was investigated. After induction of unilateral cryptorchidism, the weight of the abdominal compared with the scrotal testis declined slowly, such that by day 5 there was only a 25% reduction in weight compared with a 70% reduction by day 40. In contrast, the levels of testosterone in IF from abdominal testes declined rapidly, such that by day 5 an 80% reduction was attained, compared with scrotal testes, with little further change by day 40.(ABSTRACT TRUNCATED AT 250 WORDS)

Intratesticular factors controlling testicular function.

Although the testis is under overall control by pituitary gonadotropins, intratesticular control mechanisms are important 1) because of the unique structural organization of the testis, and 2) because of the organization and local requirements of spermatogenesis. The avascular nature of the seminiferous tubules, which comprise 90% of testicular mass in most mammals, means that their exceptionally high energy and nutritional demand has to be met by local transport in testicular interstitial fluid (IF). The rate of formation of IF is determined by capillary permeability and local control of this process is thus a prerequisite for ensuring full nutritional and hormonal support for spermatogenesis. The latter is organized into specific stages arranged in a cycle, each stage having different requirements which only local control mechanisms can ensure. In the rat, Stage VII of the spermatogenic cycle has an absolute requirement for high levels of testosterone and maintenance of such levels in the testicular IF surrounding the tubules thus constitutes a crucially important function requiring local control. Because in this situation, testosterone works via the Sertoli cell and because the testosterone is produced locally by the Leydig cells in response to luteinizing hormone (LH), it is suggested that local control of intratesticular levels of testosterone is likely to be effected by a factor (or factors) produced by the Sertoli cell which acts on the Leydig cell, and which interacts with LH to modulate the levels of testosterone in testicular IF. The possibility that "testicular luteinizing hormone releasing hormone (LHRH)" may fulfill this role is examined in detail by investigating the local effects of an LHRH agonist (LHRH-A) on testicular capillary permeability and the IF levels of testosterone in normal intact adult rats. The results show that LHRH-A has dose-dependent effects on capillary permeability and the IF levels of testosterone and that these effects are modulated according to the ambient level of LH. Alteration of the IF levels of testosterone by LHRH-A is shown to be biologically effective and to be mediated partly by direct effects on Leydig cell steroidogenesis and partly by the control of capillary permeability. The physiological implications and operation of this local mechanism are discussed.