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PubMed1982

The effects of short-term culture and perifusion on LH-dependent steroidogenesis in isolated rat Leydig cells.

Tumour Leydig cells and normal mature Leydig cells lost their steroidogenic response (pregnenolone and testosterone secretion) to LH after 24 h of culture. Immature cells showed a 2-fold increase in the basal pregnenolone secretion and no change in the LH-dependent pregnenolone secretion after 24 h of culture, whereas the LH-dependent steroidogenesis decreased after 48 h. None of the 3 cell preparations showed morphological signs of degeneration during a culture period of more than 7 days. Histochemical 3 beta-hydroxysteroid dehydrogenase activity in isolated immature Leydig cells disappeared during the first 2 days of the culture period and re-appeared after 5--7 days. Testosterone production by mature Leydig cells decreased during the first hours after exposure to LH, whereas pregnenolone secretion remained constant. From these results it was concluded that Leydig cells attached to plastic can be used for investigation of acute actions of LH on steroidogenesis. A perifusion technique for cells attached to plastic was developed and was applied to the kinetics of LH action on steroidogenesis in tumour and immature Leydig cells. The first stimulation of pregnenolone secretion occurred within 5 min, but a full stimulation was only obtained after 20--30 min. This was followed by a gradual decrease in the stimulated steroid secretion to approximately 50% after 60 min.

Animals↗
PubMed1989

Competitive experience activates testosterone-dependent social aggression toward unfamiliar males.

Male hooded rats (350 to 450 g) were castrated and given subcutaneous implants of testosterone-filled or empty Silastic tubes. Four weeks later, half of the animals with testosterone implants were housed with an animal with an empty implant and left for 6 weeks. The other animals were adapted to a food-deprivation schedule, housed in testosterone-implant/sham-implant pairs and given a series of food-competition tests. Following the competition tests, all animals were observed individually in their living cage for aggression toward an unfamiliar intruder. Within the competitive situation, animals with testosterone implants were more aggressive and more successful at maintaining access to food than their cagemates with sham implants. In the unfamiliar intruder test, animals with testosterone implants that had been subjected to food competition were more aggressive toward an unfamiliar intruder than were animals with testosterone implants that had not been given competitive experience. Animals with testosterone implants given competitive experience were more aggressive than their castrated cagemates, but animals with testosterone implants not given competitive experience were not more aggressive than their cagemates. These results demonstrate that testosterone-dependent social aggression fostered by a competitive situation is elicited by an unfamiliar male intruder. They also confirm other evidence that activation of social aggression does not appear to require increased testicular testosterone secretion.

Aggression↗
PubMed1999

Modulation of the hypothalamo-pituitary-gonadal axis and the pineal gland by neurokinin A, neuropeptide K and neuropeptide gamma.

Modulation of the hypothalamo-pituitary-gonadal axis and the pineal gland by neurokinin A, neuropeptide K, and neuropeptide gamma. PEPTIDES 1999. Neurokinin A (NKA), neuropeptide K (NPK) and neuropeptide gamma (NPG) are members of the family of tachykinins, and act preferentially on NK-2 tachykinin receptors. These peptides are widely distributed and are potent stimulators of smooth muscle contraction, especially in the respiratory and gastrointestinal tract. They also induce vasodilatation and plasma extravasation. Through their effects on the vascular tone, they are also potential regulators of the blood flow and therefore of the function of many organs and tissues. Tachykinins have been demonstrated to influence the secretory activity of endocrine cells, and they may have a physiological role as regulators of endocrine functions. A number of reports have indicated that NPK, NKA and NPG act on the hypothalamo-pituitary gonadal axis to regulate functions related to reproduction. Therefore, we thought that, at this point, it was important to review the available evidence suggesting the role of these tachykinins on reproductive functions by effects exerted at 3 different levels of regulation: the hypothalamus, the anterior pituitary and the gonads. These 3 tachykinin peptides were reported to have effects on reproductive functions, acting on the control of the secretion of gonadotropin and prolactin at the level of the hypothalamo-pituitary axis, and on the steroid secretion by the testes and the ovaries. Acting on the hypothalamus, tachykinins, mainly NPK, were reported to inhibit LH secretion, but this effect is dependent on the presence of gonadal steroids. On the anterior pituitary gland, however, tachykinins were shown to stimulate LH and prolactin secretion, and this effect is also dependent on the presence of gonadal steroids. Tachykinin concentrations in the hypothalamus and pituitary are regulated by steroid hormones. In the hypothalamus, estrogens and testosterone increase tachykinin concentration. In the anterior pituitary gland, estradiol and thyroid hormones markedly depress tachykinin concentrations. Ovariectomy and exposure to short photoperiods significantly increase anterior pituitary tachykinins in the Siberian hamster. In the pineal gland, SP and NK-1 receptors are present and, more recently, the presence of NKA and probably also NPK was demonstrated. Castration and steroid replacement modified the content of tachykinins in the pineal gland. The removal of the superior cervical ganglia was followed by an increase in NKA content in the pineal gland. These results suggest that gonadal steroids may influence tachykinins in the pineal gland. In the gonads, tachykinins stimulated the secretory activity of Sertoli cells, but inhibited testosterone secretion by Leydig cells. There are very few reports on the role of tachykinins in the ovary, but some of them indicated that these peptides are present in some of the ovarian structures, and they may affect the secretion of ovarian steroids. Thus, NKA, NPK and NPG appear to have a modulatory role, mainly acting as paracrine factors, on the hypothalamo-pituitary-gonadal axis.

Animals↗
PubMed2001

Infancy is not a quiescent period of testicular development.

Postnatal evolution of the testis in most laboratory animals is characterized by the close continuity between neonatal activation and pubertal development. In higher primates, infancy, a long period of variable duration, separates birth from the beginning of puberty. This period has been classically considered as a quiescent phase of testicular development, but is actually characterized by intense, yet inapparent activity. Testicular volume increases vigorously shortly after birth and in early infancy due to the growth in length of seminiferous cords. This longitudinal growth results from active proliferation of infantile Sertoli cells which otherwise display a unique array of functional capabilities (oestrogen and anti-müllerian hormone secretion, increase of FSH receptors and maximal response to FSH). Leydig cells also show recrudescence after birth, possibly determined by an active gonadotrophic-testicular axis which results in increased testosterone secretion of uncertain functional role. This postnatal activation slowly subsides during late infancy when periodic phases of activation of the hypothalamo-pituitary-testicular axis are paralleled by incomplete spermatogenic spurts. The beginning of puberty is marked by the simultaneous reawakening of Leydig cell function and succeeding phases of germ cell differentiation/degeneration which ultimately lead to final spermatogenic maturation. The marked testicular growth in this stage is due to progressive increase at seminiferous tubule diameter. Sertoli cells, which have reached mitotic arrest, develop and differentiate, establishing the seminiferous tubule barrier, fluid secretion and lumen formation, and acquiring cyclic morphological and metabolic variations characteristic of the mature stage. All of these modifications indicate that, far from being quiescent, the testis in primates experiences numerous changes during infancy, and that the potential for pubertal development and normal adult fertility depends on the successful completion of these changes.

Animals↗
PubMed1979

Evaluation of various doses of testosterone on accessory reproductive organs and plasma testosterone in intact and gonadectomized rhesus monkeys (Macaca mulatta).

The effect of 10 days i.m. treatment of testosterone propionate (TP) on plasma testosterone and accessory reproductive organs were studied in adult (6 to 6 1/2 kg) male rhesus monkeys, housed under natural light conditions using six different dose levels. The study was scheduled in the month of September and October. To maintain the weight of accessory reproductive organs and testosterone levels in castrates, different dose levels of exogenous testosterone propionate were required: 3.2 mg/d for seminal vesicles, 4.8 mg/d for ventral prostate and 3.2 mg/d for plasma testosterone titer. The levels of so-called "physiological" doses of exogenous testosterone varied for various target organs under consideration. TP at a dose of 0.4 mg/d had a depressing effect on plasma testosterone in intact monkeys. For higher doses, plasma testosterone increased roughly similarly in both intact and castrated monkeys. It suggests that with otherwise "physiological" doses of testosterone propionate, there is an almost complete blockage of endogenous testosterone secretion.

Animals↗
PubMed1997

Local effect of PACAP and VIP on testicular function in immature and adult rats.

PACAP, VIP, anti-PACAP and anti-VIP antisera were injected intratesticularly. In 9-day-old hemicastrated rats PACAP or VIP decreased basal testosterone secretion. In 22-day-old hemicastrates VIP but not PACAP reduced compensatory testicular hypertrophy, however, neither PACAP nor VIP altered steroidogenesis. Anti-VIP antiserum to this age group increased testosterone production and enhanced compensatory testicular hypertrophy. In adult hemicastrates neither the peptides nor the antisera influenced steroidogenesis. Neither in immatures nor in adults treatment of both testes with PACAP or VIP had any effect. Data indicate that both PACAP and VIP might exert a local action on testicular steroidogenesis, on compensatory testicular hypertrophy, and these effects are age-dependent.

Animals↗
PubMed1989

Androgens, progestagens and agonistic behaviour: a review.

The relationship between androgens, progestagens and agonistic behaviour is reviewed. Most literature concerned the effects of hormones on aggression; little information was available on hormonal influences on fear. Difference in aggression levels between males and females may be explained by assuming the existence of a gender difference in motivation, which, among other factors, is controlled by androgen and progestagen levels in peripheral blood. Androgens and progestagens are metabolised mainly by 5 alpha-reductase in the target organs. In the brain, aromatisation of testosterone also plays a role. The metabolites of testosterone may exert the same organising and activating influence as testosterone on juvenile and adult brain tissue, respectively. In some animal species testosterone secretion appears to be influenced by social and environmental variables. Conversely, alterations in plasma androgen levels have been found to affect behaviour. Dominant and/or aggressive individuals tend to show higher plasma testosterone levels than submissive and/or less aggressive animals. Among other mechanisms, competitive inhibition of androgen action at a central level, by progestagens acting as antagonists of androgens, may be important.

Aggression↗
PubMed2000

Multiple effects of retinoids on the development of Sertoli, germ, and Leydig cells of fetal and neonatal rat testis in culture.

We investigated the effect of retinoids on the development of Sertoli, germ, and Leydig cells using 3-day culture of testes from fetuses 14.5 and 18.5 days post-conception (dpc) and from neonates 3 days postpartum (dpp). Addition of 10(-6) M and 3.10(-8) M retinoic acid (RA) caused a dose-dependent disruption of the seminiferous cords in 14.5-day-old fetal testes, without any change in the 5-bromo-2'-deoxyuridine (BrdU) labeling index of the Sertoli cells. RA caused no disorganization of older testes, but it did cause hyperplasia of the Sertoli cells in 3-dpp testes. Fragmentation of the Sertoli cell DNA was not detected in control or RA-treated testes at any age studied. The cAMP produced in response to FSH was significantly decreased in RA-treated testes for all studied ages. Both 10(-6) M and 3.10(-8) M RA dramatically reduced the number of gonocytes per 14.5-dpc testis. This resulted from a high increase in apoptosis, which greatly exceeded the slight increase of mitosis. RA caused no change in the number of gonocytes in testes explanted on 18.5 dpc (the quiescent period), whereas it increased this number in testes explanted on 3 dpp (i.e., when gonocyte mitosis and apoptosis resume). Lastly, RA and retinol (RE) reduced both basal and acute LH-stimulated testosterone secretion by 14.5-dpc testis explants, without change in the number of 3beta-hydroxysteroid dehydrogenase-positive cells per testis. Retinoids had no effect on basal or LH-stimulated testosterone production by older testes. In conclusion, RE and RA are potential regulators of the development of the testis and act mainly negatively during fetal life and positively during the neonatal period on the parameters we have studied.

Animals↗
PubMed1999

Müllerian-inhibiting substance regulates androgen synthesis at the transcriptional level.

Müllerian-inhibiting substance (MIS) is a hormone produced by Sertoli cells of the fetal testes that causes regression of the Müllerian ducts, the precursors to female reproductive tract structures that are present in the bipotential urogenital ridge. MIS is also produced in the adult gonads of both males and females, albeit at much lower levels than those measured during the fetal and perinatal periods. Adult transgenic mice chronically overexpressing MIS exhibit severe gonadal abnormalities and, in males, dramatically reduced levels of testosterone, which might lead to the incomplete virilization observed in some of the males. To understand the roles played by MIS in the adult gonad, we performed Northern analyses to show that the MIS type II receptor is expressed in purified Leydig cells and in two rodent Leydig cell lines, R2C and MA-10. Addition of purified recombinant human MIS to cultures of both R2C and MA-10 cells reduced steroid production. With MA-10 cells, the reduction of testosterone secretion into the medium was reduced to 1/10th of that in the control culture, which provided us with a means to study the molecular mechanisms underlying MIS-mediated suppression of testosterone synthesis. Northern analysis revealed that after stimulation with cAMP, the expression of messenger RNA for P450c17 hydroxylaselyase, the enzyme that catalyzes the conversion of progesterone to androstenedione, was reduced to background levels in the presence of MIS. Addition of cycloheximide, a protein synthesis inhibitor, did not prevent the effect of MIS, indicating a direct effect of MIS signal transduction on the expression of P450c17. Analysis of the transcriptional activity of Cyp17, the gene for murine P450c17, with Cyp17 promoter/luciferase reporter constructs shows that MIS regulates the transcription of Cyp17 in a concentration- and time-dependent manner. From our results, we conclude that MIS might play a physiological role in maintaining testosterone homeostasis. These findings will allow us in the future to use the transcriptional regulation of Cyp17 as a model to uncover the signal transduction pathways of MIS and the molecular mechanisms of its suppression of androgen synthesis.

Androgens↗
PubMed1988

Differential suppression of testosterone and estradiol in hirsute women with the superactive gonadotropin-releasing hormone agonist leuprolide.

To determine the dose of the GnRH agonist leuprolide necessary to maximally suppress ovarian testosterone secretion, 10 moderately to severely hirsute women (5 with idiopathic hirsutism and 5 with polycystic ovarian syndrome) were given gradually increasing leuprolide doses, starting with either 5 or 10 micrograms/kg.day. Serum testosterone and estradiol, basal LH, and the LH response to GnRH were measured before and at the end of each treatment period, until maximal suppression of estradiol and testosterone occurred. Leuprolide was then continued for a total of 6 months to assess its clinical efficacy. Hirsutism scores and hair growth rates were determined before and after therapy. Serum estradiol and the LH response to GnRH were maximally or near-maximally suppressed in all women by the lowest doses of leuprolide used. Basal serum LH was not maximally suppressed in all women until a dose of 15 micrograms/kg.day was reached, and maximal testosterone suppression required 15 micrograms/kg.day or more in 7 of the 10 women. The addition of 0.5 mg dexamethasone daily for 4 weeks at the end of the study in 5 of the women reduced serum testosterone to undetectable levels. Symptomatic improvement in hirsutism occurred in 9 women, hirsutism scores decreased by at least 3 points in 5 women, and hair growth rates decreased in 8 women. These data indicate that low doses of leuprolide were sufficient to maximally suppress serum estradiol and the LH response to exogenous GnRH. Higher leuprolide doses were needed to maximally suppress serum testosterone and the basal LH levels. Leuprolide (20 micrograms/kg.day) effectively reduced hair growth in the majority of these women.

Adult↗
PubMed1994

Combined testosterone treatment in pubertal and adult periods induces male-specific acetohexamide reductase activity in liver microsomes of female rats.

The influence of testosterone treatment on acetohexamide reductase activities in liver microsomes and cytosol of female rats was examined. Acetohexamide reductase activity in liver microsomes was much lower in female rats than in male rats. Combined testosterone treatment in pubertal and adult periods induced male-specific acetohexamide reductase activity in liver microsomes of female rats. However, testosterone treatment only during puberty or during adulthood was without effect. Testosterone secreted from the testes during puberty appeared to have a significant effect similar to neonatal imprinting in the induction of acetohexamide reductase activity in liver microsomes of female rats. The combined testosterone treatment, or testosterone treatment only during puberty or during adulthood had no effect on acetohexamide reductase activity in liver cytosol of female rats.

Aging↗
PubMed1994

[Drug modulation of libido and sexual activity. Behavior effect of GnRH analog in man].

Libido and male sexual behaviour are under the control of complex testosterone-dependent neuro-endocrine mechanisms. Better knowledge of these mechanisms has allowed to modulate sexual behaviour using drugs. Indeed, it is possible to block spontaneously uncontrollable sexual pulsions of aggressive hypersexual men by dropping testosterone secretion and consecutively decreasing androgen effects on target cells. From now, mutilating neurosurgery and treatment with either estrogens or antigonadotrophic progestagens are withdrawn. Cyproterone acetate, acting as a competitive inhibitor of testosterone action through its binding to androgen receptors, has been used with efficacy in 80% of cases studied. However, the therapeutic use of cyproterone acetate is limited by three drawbacks: i/potential side effects, ii/exclusive oral route of administration and iii/lack of available biological criteria as a control of the good observance of the treatment. We studied the efficacy of a GnRH analogue (Triptoreline), which induces a reversible hormonal castration and of which both the formulation and the route of administration avoid the inconveniences linked to a treatment with cyproterone acetate. 3.75 mg triptoreline injected intramuscularly once a month had been very effective on clinical and biological parameters in 5/6 aggressive hypersexual patients. In 3 of them a previous treatment with cyproterone acetate had been uneffective. Such a reversible hormonal castration suppressing sexual addiction, would lead to favourable conditions for psychotherapy.

Adolescent↗
PubMed1984

Pituitary-testicular responses of estradiol-17 beta-implanted bull calves to continuous versus pulsatile infusion of luteinizing hormone releasing hormone.

The luteinizing hormone (LH), follicle-stimulating hormone (FSH) and testosterone response of bull calves implanted with estradiol-17 beta to continuous and pulsatile infusion of luteinizing hormone releasing hormone (LHRH) has been examined. Estradiol-17 beta reduced serum LH and FSH concentrations and suppressed testosterone secretion and testicular growth when compared with sham-implanted bulls. Pulsatile iv infusion of LHRH [500 ng every 2 h (6 micrograms/d)] for a 4-wk period to estradiol-17 beta-implanted bulls resulted in elevated mean serum LH and testosterone concentrations that were characterized by discrete secretory episodes. Mean serum FSH was also increased by LHRH pulse infusion, but LHRH-coupled secretory episodes were not apparent. Continuous infusion of LHRH (6 micrograms/d) did not increase the low serum gonadotropin levels observed in estradiol-17 beta-implanted calves. Testicular growth was normal in LHRH pulse-infused calves, but was markedly curtailed in continuously infused calves. These results suggest that estradiol-17 beta inhibits testicular development by blocking gonadotropin release at the level of the hypothalamus because pulsatile administration of LHRH can override the inhibitory effect by increasing LH and FSH secretion.

Animals↗
PubMed1984

[Dihydrotestosterone formation (5 alpha-reductase activity) in cultured human skin fibroblasts].

Testosterone secreted from the testis is converted to dihydrotestosterone (DHT) in target tissues by 5 alpha-reductase and DHT exerts its action on the nucleus. Since skin is one of the target tissues of androgen we established a system for culturing human skin fibroblasts, and we investigated the conversion of testosterone to DHT in genital and nongenital skin fibroblasts obtained from males as well as from females. In our system, fibroblasts were incubated with 0.1 microM 1, 2-3H testosterone, and labeled metabolites were separated by thin layer chromatography. DHT formation was linear for 6 hours and the rate of DHT formation correlated with the growth phase of the fibroblasts. In the course of serial subculture, DHT formation did not change between the 3rd and 10th subculture in four cell strains. DHT formation in nongenital skin fibroblasts did not differ significantly between males and females. Fibroblasts obtained from male genital skin produced significantly greater amounts of DHT than those from male or female nongenital skin. Furthermore, DHT formation in genital skin fibroblasts did not differ between normal males and hypogonadal males. These data suggest that genital skin is the target tissue where testosterone strongly converts to DHT and the difference of male secondary sexual characteristic appearance between males and females may not depend on the sensitivity of the target tissues to androgen but on the secretion rate of androgen.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1985

Direct inhibitory effects of natural and synthetic oestrogens on testosterone release from human testicular tissue in vitro.

Human testicular slices were incubated in vitro in order to examine the direct effects of natural and synthetic oestrogens on testosterone secretion. In the presence of human chorionic gonadotrophin (10 IU per ml), oestradiol-17 beta (1 or 10 micrograms per ml) and ethinyl oestradiol (0.1, 1 or 10 micrograms per ml) inhibited testosterone release into the media in a dose dependent manner. The addition of estramustine phosphate, estromustine, diethylstilboestrol or diethylstilboestrol diphosphate in comparable concentrations produced no significant effects on testosterone release.

Adenocarcinoma↗
PubMed2000

Human chorionic gonadotropin with C-elongated alpha-subunit retains full receptor binding and partial agonist activity.

OBJECTIVE: To test whether extension of the C-terminus of human chorionic gonadotropin (hCG) alpha-subunit (halpha) alters the bioactivity of the recombined alphabeta heterodimer. DESIGN: The stop codon of halpha was mutated to produce a 24 amino acid extension. METHODS: The extended halpha (alpha(+24)) was co-expressed with hCGbeta in COS-7 cells and the receptor binding and in vivo bioactivity of the secreted hormone was compared with its wild-type counterpart. RESULTS: This extension did not impair the binding of hCG to rat LH/CG receptors and provoked a sixfold reduction in its stimulatory activity of testosterone secretion in rat Leydig cells. CONCLUSIONS: The extension of alpha by itself does not lead to inhibition of the alphabeta heterodimer to LH receptors but the structure of the extension appears to play an important role. It is thus possible that one-chain hCG chimeras with the beta N-terminus fused to the alpha C-terminus might be active.

Amino Acid Sequence↗
PubMed1983

Interactions of follicle-stimulating hormone and luteinizing hormone in controlling estradiol synthesis by the testis of the infant rat.

Experiments were conducted to assess the relative contribution of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) to the regulation of estradiol secretion by the testis of the 12-day-old rat. In an in vivo model system, stimulation of the whole testis with NIH-FSH-S13 (5% LH activity) caused an 8-fold increase in testosterone secretion within 1 h followed by a 5-fold increase in estradiol secretion. Qualitatively, similar findings were obtained from whole testes incubated in tissue culture medium 199. The in vitro system was used to further examine the response of the testes to LH and FSH. Testes exposed to a variety of doses of LH or 10 ng/ml of highly purified FSH (3 X 13, 1% LH activity) showed no change in estradiol secretion. However, a synergistic effect was observed when purified FSH and LH were combined, provided the LH concentration exceeded 25 pg/ml. It is suggested that FSH secretion in infant rats maintains the aromatizing capacity of the seminiferous tubule at a level such that availability of aromatizable substrate becomes a major factor in the rate of tubular estrogen formation.

Animals↗
PubMed2004

Role of the adrenal gland in early post-hatching differentiation of alternative male phenotypes in the tree lezard (Urosaurus ornatus).

During development, sex steroids are important in establishing differences between males and females. However, sex steroids also are involved in the development and maintenance of individual differences in morphology and behavior within each sex. As adults, male tree lizards (Urosaurus ornatus) exhibit alternative reproductive tactics correlated with dewlap (throat fan) coloration. Males with orange-blue dewlaps are aggressive and territorial, whereas males with orange dewlaps are less aggressive and employ a satellite strategy. Dewlap coloration develops within the first 90 days after hatching and remains fixed throughout life. Recent work demonstrates that individual males differ in progesterone and testosterone secretion during development, suggesting that these hormones regulate the development of alternative male phenotypes. The current work uses in vitro incubation of adrenal and gonadal tissues to identify the source of progesterone and testosterone during the period of male differentiation and to follow ontogenetic changes in hormone release. The results indicate that, in all developmental stages sampled, adrenal incubations primarily contain progesterone and corticosterone whereas gonadal incubations contain primarily testosterone. These data indicate that the hatchling adrenal is the primary source of progesterone during early post-hatching development. Since progesterone has been demonstrated to play a role in the establishment of individual differences in morphology and behavior in male tree lizards, our results suggest that the hatchling adrenal gland plays an important role in post-hatching development of alternative male phenotypes.

Adrenal Glands↗