Injection Of Testosterone Propionate Research Articles

Effects of chronically high doses of the anabolic androgenic steroid, testosterone, on intermale aggression and sexual behavior in male rats

To determine if chronic exposure to high doses of anabolic androgenic steroids (AAS) increase aggression and sexual activity in gonadally intact rats, we administered SC injections of testosterone propionate (TP: 1 mg) or propylene glycol (PG: as a vehicle control) three times per week for 10 consecutive weeks. Weekly tests for male copulation were conducted by pairing each male with a sexually receptive female in a glass arena and recording various parameters of copulation. Chronic treatment with TP did not alter any parameter of male copulation including ejaculation and post ejaculatory interval. Sexually experienced males were tested once per week for intermale aggression in a neutral environment. For aggression tests, each experimental animal was placed into an arena with an opponent male for 15 min. The opponent, a gonadally intact male, was used only for the purpose of the aggression test. Frequencies of dominance, submissive, threat, and fight postures, as well as approaches were scored for each animal. TP-treated males did not differ in body weight from PG-treated males, suggesting that the increased aggression was not due to increased body mass. The results of this study show that chronic exposure to the anabolic androgenic steroid, testosterone, potentiates male aggressive response patterns but does not alter male sexual behavior or body weight.

In vitro fertilization of androgen sterilized mice

In order to explore the effect of neonatal androgen administration on oocyte quality, ovulation induction and in vitro fertilization (IVF) were performed in androgen-sterilized mice. Androgen sterilized mice were produced by the subcutaneous injection of testosterone propionate (TP) at 5 days of age and ovulation induction was performed by pregnant mare's serum gonadotropin (PMSG)-human chorionic gonadotropin (hCG) treatment at 9 to 13 weeks old. The number of oocytes ovulated in TP-injected mice was 19.9 ± 2.0 (Mean ± SE) and was significantly less than that in normal mice (37.8±1.9; P<0.01). The fertilization rate of oocytes retrieved from TP-treated mice (38.8%) was significantly lower than that from normal mice (60.3%; P<0.01). These results indicate that neonatal androgen treatment has a detrimental effect on oocyte maturity.

Dihydrotestosterone-sensitive neurons in the male rat ventromedial hypothalamus

Electrical stimulation of the midbrain central gray caused antidromic activation in 273 neurons in and around the hypothalamic ventromedial nucleus in 40 urethan-anesthetized male rats. The latency (range: 2–39 ms) and threshold (100–1,600 μA) of the responses were compared among intact males and orchidectomized males, which received either no treatment, daily injections of testosterone propionate or dihydrotestosterone, or a combined estradiol benzoate and progesterone injection. Recordings were from comparable neuronal pools, because probability distribution for the latency as well as histological localization of each response were not different among groups. Orchidectomy decreased the mean threshold, and either treatment reversed the effect. Dihydrotestosterone increased the mean threshold by reducing the number of cells with thresholds below 600 μA, to a level as in intact males. Estrogen reduced the number of cells responding at 300–900 μA, but at lower thresholds, fell short of replicating the distribution in intact males. Testosterone reinstated the distribution as in intact males. It was concluded that different subgroups of ventromedial hypothalamic neurons with specific sensitivity to metabolites of testosterone project to the central gray.

Formation of Neurons in the Sexually Dimorphic Anteroventral Periventricular Nucleus of the Preoptic Area of the Rat: Effects of Prenatal Treatment with Testosterone Propionate

An examination was made of neurogenesis in the anteroventral periventricular nucleus (AVPv) of the preoptic area of the rat using bromodeoxyuridine (BrdU), a thymidine analog, and a BrdU-specific antibody. Cells in the AVPv of adult rats were labeled with the antibody when BrdU was injected into pregnant rats once during day 13 to 18 of gestation, but not during day 10 to 12 nor 19 to 20 of gestation nor on postnatal day 1, indicating the neurogenesis of the AVPv occurs during a limited period from day 13 to 18 of gestation. Next, to examine the effects of androgen on neurogenesis, BrdU was injected once on day 15 into pregnant rats that also received injections of testosterone propionate (TP). The number of BrdU-labeled cells in the AVPv was similar in control female and male fetuses and female fetuses from pregnant rats that received daily injections of TP during days 14 to 16, when fetuses were examined on day 17 of gestation. These results suggest that the neurogenesis that was recognized by labeling with BrdU was not affected by the treatment with TP. On day 21 of gestation, BrdU-labeled cells in the AVPv of control male fetuses and female fetuses that received TP during days 14 to 18 were fewer in number than those in female fetuses of the control group, whereas treatments with TP during days 14 to 16 and during days 17 to 18 did not cause any significant decrease in number of BrdU-labeled cells. These findings can support the hypothesis that elimination of a population of cells, for example, by cell death as described previously, is enhanced in male fetuses and in female fetuses treated with TP repetitively.

Sex differences in the anteroventral periventricular nucleus of the preoptic area and in the related effects of androgen in prenatal rats

The density of cells in the anteroventral periventricular nucleus (AVPv) of the preoptic area of female rats was greater than that of males on day 21 of gestation. It appears that this difference between the sexes is caused by the action of androgen since the density of cells in the AVPv of female fetuses fell to the density in males when the mother received injections of testosterone propionate (TP) on days 14–18 of gestation. Pycnotic cells were more frequently found in oil-treated control males and TP-treated female fetuses than in control female fetuses. This result suggests that the prenatal injections of TP enhanced the rate of degeneration of the cells in the AVPv.

Hormone-sensitive periods for the control of motoneuron number and soma size in the dorsolateral nucleus of the rat spinal cord

The dorsolateral nucleus (DLN) of the rat lumbosacral spinal cord is sexually dimorphic, with males having more and larger DLN motoneurons than do females. The development of this dimorphism depends on the presence of perinatal androgens. The present study sought to determine the periods in development during which the DLN is sensitive to the masculinizing effects of the androgen testosterone propionate (TP). The size and number of DLN motoneurons in neonatally ovariectomized female rats that were exposed to TP during either the late prenatal, early postnatal, or late postnatal period were compared to control males and females. Both late prenatal and early postnatal TP injections significantly increased DLN number by 48% and 50%, respectively, but the sensitive period for TP masculinization of soma size seems to be primarily postnatal, because prenatal TP injections had little or no effect on that measure. The sensitive period for TP masculinization of DLN neuron number is similar to that of the sexually dimorphic spinal nucleus of the bulbocavernosus (SNB). However, the sensitive period for TP masculinization of DLN soma size appears to begin later than for the SNB.

Further evidence that prolactin secretion in adult female rats is differently modified after neonatal estrogenization or androgenization: Responses to methysergide, quipazine, and pizotifen

The role of the serotoninergic system in the control of prolactin secretion was investigated in adult female rats treated on the first day of life with estradiol benzoate (EB) (100 μg), testosterone propionate (TP) (25 or 100 μg), or olive oil. Blood of rats was obtained through a chronic intraatrial cannula at 0, 30, 60, 90, and 120 min after the IP administration of the serotoninergic blockers methysergide (0.75, 2.5, and 7.5 mg/kg) or pizotifen (2 mg/kg), the agonist quipazine (3 or 30 mg/kg), or saline. We have found that 1) the anovulatory syndrome induced by EB or 100 μg injection of TP was associated with hyperprolactinaemia, whereas normal prolactin concentrations in plasma were observed in females injected with 25 μg of TP; 2) methysergide administration increased plasma prolactin concentrations in control and androgenized females but not in the estrogenized ones. This different response may be related to the antidopaminergic action of methysergide, because both estrogenized and androgenized females responded similarly after pizotifen injection; 3) after quipazine injection, an initial stimulation was observed in females injected with estradiol or 100 μg of TP, but not in other groups, whereas a delayed inhibition occurred in androgenized females. These results suggest that the effects of estrogenization and androgenization both the dopaminergic and serotoninergic control of prolactin secretion are qualitatively different.

Reversal of reproductive deficiency in the hpg male mouse by neonatal androgenization.

Some aspects of reproductive function in the GnRH-deficient hypogonadal (hpg) mutant mouse can be restored by transplanting normal fetal brain tissue containing GnRH cells into the central nervous system of adult hpg mice. However, hpg males showing physiological response to the graft fail to display sexual behavior and are infertile. We hypothesized that the reproductive deficit of these males is due to insufficient perinatal exposure to testicular androgens as a consequence of the GnRH deficiency. To test this hypothesis we androgenized hpg males by giving them neonatal injections of testosterone propionate (TP). Controls consisted of hpg males not androgenized neonatally and of normal males. All three groups received a TP implant in adulthood, and their copulatory behavior and reproductive capability were recorded. In addition, other hpg males, not androgenized neonatally, received fetal brain transplants containing GnRH neurons and were also tested for copulatory behavior and reproductive capability before and after receiving a TP implant. Three of 8 neonatally androgenized hpg males expressed the full repertoire of male sexual behavior, including intromission and ejaculation, and sired several litters. Three of 7 control hpg males that were not androgenized neonatally but received TP implants in adulthood also displayed mounting and intromission, but there was no evidence of ejaculation, and these males failed to impregnate normal females. Of the 8 hpg males that responded to a fetal transplant with testicular growth, only 1 displayed mounting behavior. However, when given a TP implant, 4 of 8 hpg males with grafts displayed mounting and intromissions.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of sex and androgen treatment on dendritic dimensions of neurons in the sexually dimorphic preoptic/anterior hypothalamic area of male and female ferrets.

A sexually dimorphic group of cells at the dorsal border of the preoptic/anterior hypothalamic area (POA/AH) of ferrets has been previously identified in Nissl-stained tissue. In this study, Golgi-stained tissue was examined in order 1) to determine whether sex differences exist in dendritic dimensions of neurons from this region, and 2) to assess the effects of adult androgen treatment on dendritic morphology in ferrets of both sexes. Brains from adult ferrets given daily injections of testosterone propionate (5 mg/kg body weight) or oil vehicle for 5 weeks after gonadectomy were impregnated by Golgi-Cox procedures. After sectioning at 120 microns, 78 multipolar neurons were selected from the sexually dimorphic POA/AH of 12 ferrets and reconstructed in three dimensions with the aid of a computer-assisted neuron tracing system. Large sex differences were observed in somal area and most aspects of dendritic morphology, including total length, number of branches, and total dendritic surface area. Androgen also appeared to accentuate dendritic arborization in both sexes, but this effect was weaker than the sex effect, more apparent in males than females, and restricted to fewer variables. The most statistically significant effects of adult androgen treatment in males were found for total dendritic surface area and percentage of fourth order dendrites, and in females, average dendritic thickness. These data show that strong sex differences exist in dendritic structure of neurons in the POA/AH, and suggest that alterations in levels of gonadal steroids in adulthood may promote synaptic remodeling in a region of the brain involved in the control of sexually dimorphic behaviors.

Maintenance of androgen-, glucocorticoid- or estrogen-responsive growth in shionogi carcinoma 115 subline sustained in castrated mice with high dose of estrogen for 30 generations (3 years).

Shionogi carcinoma 115 (SC115), an androgen‐dependent mouse mammary tumor, rapidly loses its androgen responsiveness after androgen withdrawal. The growth of this tumor can also be stimulated by high doses of estrogen or glucocorticoid. In the present study, the maintenance of hormone‐responsive growth of SC115 tumors with a high dose of estrogen was examined in castrated male mice using an SCI 15 subline obtained by serial transplantations of SCI 15 tumors in estrogen‐treated castrated mice for 3 years (30 generations) (subline E2). Seed tumors from both SC115 and subline E2 could rapidly grow in castrated mice given daily injections of testosterone propionate (TP), 17β‐estradiol (E2), or dexamethasone (Dex) (100 μg/mouse/day) but not in those given vehicle alone. Although SCI 15 and subline‐E2 tumors grown with TP or Dex showed temporary regression after steroid withdrawal, the tumors grown with E2 did not show such temporary regression. The TP‐, E2‐, or Dex‐induced growth of subline‐E2 tumors was almost the same as that of the original SCI 15 tumors. However, responsiveness to androgen, estrogen or glucocorticoid of both tumors disappeared within one passage in steroid‐depleted castrated mice. The present findings demonstrate that the loss of responsiveness to androgen as well as to high doses of estrogen or glucocorticoid of SCI 15 tumors can be prevented in castrated mice not only with androgen but also with high doses of estrogen.

Early Postnatal Androgenization Imprints Selective Changes in the Action of Estrogens in the Rat Uterus1

Exposure of animals perinatally to some hormonally active agents may imprint permanent changes on the action of related hormones. The present study investigated the effects of early postnatal androgenization on various genomic responses to estrogen in the uterus of prepubertal rats. Female rats were androgenized at postnatal ages of 1, 5, or 13 days with a single s.c. injection of testosterone propionate. At the age of 21 days, the animals were stimulated with estrogens. The uteri of androgenized and control rats were analyzed morphometrically to measure genomic parameters of estrogen stimulation in the uterus. The results demonstrate that early postnatal androgenization does not equally affect all uterine cell types and that the effects of androgenization change according to the age at androgenization. The dissociation between the various responses according to the time of androgenization suggests that there are critical ages at which the uterine cell types that respond to estrogens can be altered permanently by imprinting. The finding of changes in the action of estrogen induced by androgenization at older than neonatal ages in the rat suggests that similar changes may occur in humans exposed to androgens during their extrauterine life. This result also points to the need for further studies using the rhesus monkey because of its close resemblance to the human with respect to female reproductive physiology.

Effects of androgen treatment on adenylate cyclase system in rat hepatic membranes.

Effects of androgen treatment of young female rats on glucagon- and catecholamine-sensitive adenylate cyclase activity and adrenergic receptors of hepatic membranes have been studied. Injections of testosterone propionate for 7 days showed a significant decrease in the adenylate cyclase activity responding to isoproterenol and glucagon. The decrease in hormonal stimulation of the enzyme was accompanied with the fall in activation by non-hormonal stimuli, such as forskolin, sodium fluoride, Gpp(NH)p and Mn, without any changes in the number and the affinity of beta-adrenergic receptors of the membrane. These results suggest that androgens exert post-receptor effects by inhibiting the activity of the catalytic unit of adenylate cyclase system in rat hepatic membranes.

Testosterone-induced development of the rat levator ani muscle

The perinatal development of the levator ani (LA) muscle in male and female rats was investigated by measuring the total number of muscle units (MU) (i.e., mononucleate cells, clustered or independent myotubes, and muscle fibers) in transverse semithin sections of the entire muscle and the MU cross-sectional area in 22-day-old fetuses (F22), 1-day-old (D1 = day of birth), 3-day-old (D3), and 6-day-old (D6) newborns. Male muscle contained 350 ± 64 MU on F22, twice that of the female. The number of MU increased markedly in males from F22, but changed little in females; the number of MU in males was 760% that of females on D6. The MU cross-sectional area was greater in males on F22 (120.8 μm 2 ± 7.5) and D1 (155.2 μm 2 ± 64.8) than in females (F22: 89.2 μm 2 ± 14.2, D1: 64.1 μm 2 ± 19.7) and dropped to about 30 × μm 2 in both sexes on D6. Female rats given a single injection of testosterone propionate (TP) before D7 showed a significant increase in the number of fibers, but no increase in cross-sectional area. TP given after D7 had no effect on the fiber number, but increased the average cross-sectional area. The increase in fiber number induced by postnatal TP treatment was a permanent effect, still quantifiable in 15-month-old females. We conclude that the sexual dimorphism of the rat LA muscle is principally due to a dramatic increase in the MU number in male muscles during the perinatal period, rather than to involution of the fibers in female muscles as it is widely accepted. This increase seems to be, at least partly, under the control of testosterone.

Pretranslational Enhancement of Epidermal Growth Factor Receptor by Direct Effect of Testosterone in Mouse Liver

The effects of testosterone on the levels of epidermal growth factor receptor (EGFR) in mouse liver were studied. Orchiectomy resulted in 39% and 41% reductions in the levels of EGFR mRNA and EGF binding, respectively, within 2 weeks. Treatment of orchiectomized mice with a sc injection of testosterone propionate (TP; 100 micrograms/mouse.day) for 1 week restored these values to normal male levels. The hepatic levels of EGFR mRNA and EGF binding in females were 37% and 36% of those in males, respectively, and were not affected by ovariectomy, whereas treatment of females with TP (100 micrograms/mouse.day) increased EGFR to normal male levels within 1 week. On the other hand, neither orchiectomy nor androgen treatment affected levels of mRNAs for EGFR in the kidney or mRNAs for the structural protein beta-actin in the liver. To examine whether testosterone directly increased EGFR levels in the liver, TP (1.0 mg) pellets were implanted into the spleen of orchiectomized mice, so that testosterone released from the pellets reached the liver through the portal vein but did not enter the systemic circulation due to rapid clearance by the liver. The heptic levels of EGFR mRNA and EGF binding in orchiectomized mice were restored to normal male levels by intrasplenic implantation of TP (1.0 mg) pellets. This treatment also increased the hepatic levels of EGFR mRNA and EGF binding in female mice by 61% and 68%, respectively. In addition, sialoadenectomy, which reduced plasma EGF, as well as EGF antiserum treatment did not affect the androgen-dependent increase in EGFR levels in the liver, suggesting that endogenous EGF is not involved in the androgenic regulation of hepatic EGFR levels. These results suggest that hepatic EGFR levels are at least in part regulated at a pretranslational level by direct effects of androgens on the liver.

Corpus callosum: Interactive effects of infantile handling and testosterone in the rat.

Previous research found that the corpus callosum of male rats is larger than that of females; handling rats in infancy enhances this sex difference; and female rat pups, when handled in infancy and given 1 injection of testosterone propionate (TP) on Day 4 of life, will have callosa as large as those of males. In 2 experiments, male pups were castrated on Day 1 or received sham surgery; female pups were injected with TP on Day 4 or received an oil injection. Litters were handled or nonhandled. The previous finding that females, when handled and given TP in infancy, have a larger callosum was confirmed; however, a TP effect when administered to nonhandled females was not found. Because handling is known to cause a corticosterone release, these findings were interpreted as evidence of a developmental interaction between adrenal and gonadal hormones at the cortical level.

Plasma LH, FSH and testosterone concentrations in adult rams which were homozygous carriers or non-carriers of the Booroola fecundity gene

No gene-specific differences were found with respect to LH or testosterone pulsatile secretion (over 12 h), or in 12 hourly mean FSH concentrations in adult Booroola FF and ++ rams. Also, no differences between genotypes in the LH response to an injection of testosterone propionate, the FSH response to an infusion of bovine follicular fluid, or the testosterone response to injections of PMSG were noted. However, during the phase of seasonal testicular development, mean testosterone pulse amplitude (over 12 h) and the FSH response to 25 micrograms GnRH were higher in FF than in ++ rams (P less than 0.05); there were also significant effects of sire (P less than 0.05 in FF genotype only) and litter size (P less than 0.05) on testosterone pulse amplitude and GnRH-stimulated FSH release, respectively. During the breeding season, mean LH, but not FSH, concentrations were higher in FF than in ++ rams, after an injection of 0.5 micrograms GnRH; LH release was not affected by sire or litter size (P greater than 0.05). Long-term studies revealed that the FF rams were born in significantly larger litters, they weighed significantly less than ++ rams (P less than 0.05), and that bodyweight was significantly correlated (P less than 0.05) with litter size. There were no differences in testis size, and testis size was not significantly correlated with bodyweight. There was a strong tendency (P = 0.056) for overall mean FSH concentrations, measured weekly for 9 months, to be highest more often in FF than in ++ rams.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurokinin A levels in the hypothalamus of rats and mice: Effects of castration, gonadal steroids and expression of heterologous growth hormone genes

Neurokinin A is a decapeptide with pharmacological activities and localizations similar to those of substance P. In this report we describe the effects of castration and administration of testosterone, dihydrotestosterone and estradiol, on neurokinin A levels in the hypothalamus of male rats. The effects of estradiol and testosterone on hypothalamic neurokinin A were also examined in normal mice and in transgenic mice carrying the genes for human or bovine growth hormone (hGH, bGH, respectively). Either acute or prolonged castration was followed by a decrease of neurokinin A concentrations in the hypothalamus of male rats. The substitutive administration of testosterone propionate or estradiol benzoate for 14 days resulted in an increase of hypothalamic neurokinin A levels above the values found in intact animals. A lower dose of testosterone propionate or dihydrotestosterone also increased hypothalamic neurokinin A levels in the hypothalamus of castrated rats. In normal intact male mice a single injection of estradiol benzoate significantly increased hypothalamic neurokinin A levels. A similar effect was observed in transgenic mice carrying the bGH gene with phosphoenolpyruvate carboxykinase (PEPCK) promoter, while mice carrying the hGH gene failed to show any response to estradiol. In castrated male mice, either normal or transgenic, carrying the bGH gene with metallothionein promoter, a single injection of testosterone propionate significantly increased neurokinin A levels in the hypothalamus. It is concluded that sex steroids may regulate the levels of neurokinin A in the hypothalamus of rats and mice.

Testosterone elevates pituitary prolactin content of long‐term castrated rats under constant but not under periodic light

Intact and castrated male rats were kept for 1 week under constant or periodic light, during which time they received daily injections of either vehicle or testosterone propionate (125 or 250 micrograms day-1). Immediately after the experiment the rats were decapitated and serum and pituitary prolactin were measured radioimmunologically. The pituitary prolactin content was decreased after castration in both lighting conditions. Daily testosterone injections elevated the pituitary prolactin content of the castrated rats to the level of the intact rats in constant-light conditions but were ineffective under periodic light. Serum prolactin concentrations were not affected by constant light. We have previously shown that testosterone decreases the serum luteinizing hormone concentration of castrated rats more effectively under constant than under periodic light. In the present study we showed that serum prolactin was not elevated in constant light and thus could not be the cause of increased testosterone sensitivity. We also showed that testosterone elevates the pituitary prolactin content of castrated rats under constant but not under periodic light. This finding gives further support to the hypothesis that constant light sensitizes the hypothalamo-pituitary axis of castrated male rats to the effects of testosterone.

Divergent Regulation of Gonadotropin Subunit mRNA Levels by Androgens in the Female Rat1

To examine the effects of gonadal steroids on the pretranslational regulation of the gonadotropin subunits in the female, adult female rats, beginning 7 or 28 days after ovariectomy, received daily injections of testosterone propionate (T), dihydrotestosterone propionate (D), or estradiol benzoate (E) for 7 days. Intact cycling females and ovariectomized rats that received vehicle served as controls. Serum was obtained for LH and FSH levels to assess changes in gonadotropin secretion. Total RNA from individual rats was recovered and analyzed by blot hybridization with specific radiolabeled cDNA probes for the alpha, LH beta, and FSH beta subunits. Autoradiographic bands were quantitated and standardized to mRNA levels in the intact animals. Ovariectomy resulted in a rise in serum gonadotropin levels and all three gonadotropin subunit mRNA levels. Estrogen replacement resulted in suppression of alpha, LH beta, and FSH beta mRNAs whether given at 7 or 28 days after ovariectomy. In contrast, whereas androgen replacement decreased alpha and LH beta mRNAs, D or T did not consistently suppress FSH beta mRNAs. We conclude that chronic estrogen administration to the castrated female rat uniformly suppresses all three gonadotropin subunit mRNA levels. In female rats, as in male rats, chronic androgen administration fails to negatively regulate FSH beta mRNAs.

Sexual dimorphism in brain weight of meadow voles: role of gonadal hormones

In most adult mammals, brain weights of males exceed those of females. The role of androgens in the genesis of this sex difference was assessed in meadow voles by acute neonatal or chronic postweaning manipulation of testosterone titers. Female voles given a single injection of testosterone propionate (TP) on the second day of postnatal life had brain weights in adulthood that were indistinguishable from those of male voles and significantly heavier than those of control females. Whole brain DNA content, a measure of cell number, was not increased by neonatal TP treatment. Females treated with TP from day 19 to 70 had lower brain weights than control females and males gonadectomized at 19 days of age had greater brain weights than did intact male voles at day 70. The sex dimorphism in brain weight reflects organizational effects of testosterone during perinatal development. Beginning at weaning, and continuing through postpubertal development, testosterone decreases brain weight in both sexes. We suggest that testosterone affects brain weight by altering cell size or non-cellular components rather than cell number.