Fluctuations in plasma testosterone levels in adult male rats and mice

Sexual dimorphism in cortical bone size and strength but not density is determined by independent and time-specific actions of sex steroids and IGF-1: evidence from pubertal mouse models

Although it is well established that males acquire more bone mass than females, the underlying mechanism and timing of this sex difference remain controversial. The aim of this study was to assess the relative contribution of sex steroid versus growth hormone-insulin-like growth factor 1 (GH-IGF-1) action to pubertal bone mass acquisition longitudinally in pubertal mice. Radial bone expansion peaked during early puberty (3 to 5 weeks of age) in male and female mice, with significantly more expansion in males than in females (+40%). Concomitantly, in 5 week old male versus female mice, periosteal and endocortical bone formation was higher (+70%) and lower (-47%), respectively, along with higher serum IGF-1 levels during early puberty in male mice. In female mice, ovariectomy increased radial bone expansion during early puberty as well as the endocortical perimeter. In male mice, orchidectomy reduced radial bone expansion only during late puberty (5 to 8 weeks of age), whereas combined androgen and estrogen deficiency modestly decreased radial bone expansion during early puberty, accompanied by lower IGF-1 levels. GHRKO mice with very low IGF-1 levels, on the other hand, showed limited radial bone expansion and no skeletal dimorphism. From these data we conclude that skeletal sexual dimorphism is established during early puberty and depends primarily on GH-IGF-1 action. In males, androgens and estrogens have stimulatory effects on bone size during late and early puberty, respectively. In females, estrogens limit bone size during early puberty. These longitudinal findings in mice provide strong evidence that skeletal dimorphism is determined by independent and time-specific effects of sex steroids and IGF-1.

Results of treatment with tamoxifen in oligozoospermic men

15 men, aged 32-42, with normo- and hypogonadotropic oligozoospermia were treated with the non-steroidal compound tamoxifen. The therapeutic period lasted for 6 month and tamoxifen was administered orally in a daily dose of 2 X 10 mg. The seminal and hormonal parameters were evaluated. A significant increase in sperm density was only found in responders. The compound showed no effect in men having a hypergonadotropic stage. The changes in endocrine parameters as levels of plasma testosterone, estradiol and gonadotropins were similarly affected in "responders" and "non-responders". Treatment with tamoxifen revealed no side effects regarding sexual behaviour, development of gynecomastia or nipple pains.

The endocrine status of gossypol - treated male rats

Male adult Wistar rats were exposed daily or every other day to oral gossypol acetic acid (GAA) concentrations of 2.5-30 mg/kg for 10-20 weeks. Controls received the GAA-suspension medium or were left completely untreated. The serum concentrations of testosterone, LH and FSH as well as the weight of testis, epididymis, prostate, seminal vesicle, coagulating gland, and pituitary were determined. The accessory sex organs were prepared for light microscopy. Significant antifertility effect in these animals was achieved at GAA-dosage of 15 mg/kg and higher. GAA-administration neither altered the serum hormonal profiles nor the reproductive organ weights in comparison to the controls. Accordingly, light microscopical examination revealed no alterations in the histological picture of prostate, seminal vesicle and coagulating gland when compared with the controls. The results indicate that GAA does not interfere with the hypothalamic-pituitary-gonadal axis in male adult rats.

Androgen receptor expressing neurons that project to the paraventricular nucleus of the hypothalamus in the male rat

Androgen receptors are distributed throughout the central nervous system and are contained by a variety of nuclei that are known to project to or regulate the paraventricular nucleus (PVN) of the hypothalamus, the final common pathway by which the brain regulates the hypothalamic-pituitary-adrenal (HPA) response to homeostatic threat. Here we characterized androgen receptor staining within cells identified as projecting to the PVN in male rats bearing iontophoretic or crystalline injections of the retrograde tracer FluoroGold aimed at the caudal two-thirds of the nucleus, where corticotropin-releasing hormone-expressing neurons are amassed. Androgen receptor (AR) and FluoroGold (FG) double labeling was revealed throughout the limbic forebrain, including scattered numbers of cells within the anterior and posterior subdivisions of the bed nuclei of the stria terminalis; the medial zone of the hypothalamus, including large numbers of AR-FG-positive cells within the anteroventral periventricular and medial preoptic cell groups. Strong and consistent colabeling was also revealed throughout the hindbrain, predominantly within the periaqueductal gray and the lateral parabrachial nucleus, and within various medullary cell groups identified as catecholaminergic, predominantly C1 and A1 neurons of the ventral medulla. These connectional data predict that androgens can act on a large assortment of multimodal inputs to the PVN, including those involved with the processing of various types of sensory and limbic information, and provide an anatomical framework for understanding how gonadal status could contribute to individual differences in HPA function.

Effects of mild calorie restriction on reproduction, plasma parameters and hepatic gene expression in mice with altered GH/IGF-I axis

The somatotropic axis, the hypothalamic-pituitary-gonadal axis and the nutritional status are deeply interrelated in mammals. Calorie restriction (CR) prolongs lifespan, but usually at some cost to reproduction. Interestingly, many of the physiological characteristics of animals with interruption in the somatotropic axis are shared by CR animals. The level of CR in most studies is 30-60%. We tested if a milder (20%) CR would promote health benefits without inhibiting reproduction in four types of mice with altered somatotropic axis: Ames dwarfs, GHR-KO, and PEPCK-bGH and MT-bGH transgenics. Fertility was not altered by CR in any of the examined groups. Mild CR did not affect final body weights or relative reproductive organ weights; did not alter plasma levels of glucose, insulin, IGF-I, testosterone, progesterone or estradiol; and did not influence hepatic expression of genes related to longevity. Altered activity of the GH/IGF-I axis in the different mice models studied had a major impact on the parameters analyzed. This preliminary study encourages speculation that mild regimens of CR can produce health and longevity benefits without the "costs" of impaired reproductive potential.

Arsenic-induced toxicity and the protective role of ascorbic acid in mouse testis

Oxidative stress has been suggested to be a major cause of male reproductive failure. Here, we investigated whether arsenic, which impairs male reproductive functions in rodent models, acts by inducing oxidative stress. Male 8-week-old ICR mice were given drinking water containing 20 or 40 mg/l sodium arsenite with or without 0.75 or 1.5 g/l of the antioxidant ascorbic acid for 5 weeks. The arsenic-treated mice showed decreased epididymidal sperm counts and testicular weights compared to untreated mice. These effects were reversed in mice that were co-treated with ascorbic acid. Similarly, arsenic treatment lowered the activities of testicular 3beta-hydroxysteroid dehydrogenase (HSD) and 17beta-HSD, which play important roles in steroidogenesis, and this was reversed by co-treatment with ascorbic acid. The testicles of arsenic-treated mice had decreased glutathione (GSH) levels (which correlate inversely with the degree of cellular oxidative stress) and elevated levels of protein carbonyl (a marker of oxidative damage to tissue proteins). Ascorbic acid co-treatment reversed both of these effects. Thus, ascorbic acid blocks both the adverse effects of arsenic on male reproductive functions and the arsenic-induced testicular oxidative changes. These observations support the notion that arsenic impairs male reproductive function by inducing oxidative stress.

Replacing the mouse androgen receptor with human alleles demonstrates glutamine tract length-dependent effects on physiology and tumorigenesis in mice

Polymorphism in the length of the N-terminal glutamine (Q) tract in the human androgen receptor (AR) has been implicated in affecting aspects of male health ranging from fertility to cancer. Extreme expansion of the tract underlies Kennedy disease, and in vitro the AR Q tract length correlates inversely with transactivation capacity. However, whether normal variation influences physiology or the etiology of disease has been controversial. To assess directly the functional significance of Q tract variation, we converted the mouse AR to the human sequence by germline gene targeting, introducing alleles with 12, 21, or 48 glutamines. These three "humanized" AR (h/mAR) mouse lines were grossly normal in growth, behavior, fertility, and reproductive tract morphology. Phenotypic analysis revealed traits that varied subtly with Q tract length, including body fat amount and, more notably, seminal vesicle weight. Upon molecular analysis, tissue-specific differences in AR levels and target gene expression were detected between mouse lines. In the prostate, probasin, Nkx3.1, and clusterin mRNAs trended in directions predicted for inverse correlation of Q tract length with AR activation. Remarkably, when crossed with transgenic adenocarcinoma of mouse prostate (TRAMP) mice, striking genotype-dependent differences in prostate cancer initiation and progression were revealed. This link between Q tract length and prostate cancer, likely due to differential activation of AR targets, corroborates human epidemiological studies. This h/mAR allelic series in a homogeneous mouse genetic background allows examination of numerous physiological traits for Q tract influences and provides an animal model to test novel drugs targeted specifically to human AR.

Cholesterol substrate pools and steroid hormone levels are normal in the face of mutational inactivation of NPC1 protein

Mutational inactivation of NPC1 largely blocks the movement of LDL-derived cholesterol from the lysosome to the metabolically active, cytosolic pool of sterol that is the substrate for steroid hormone production. Such a block might, in theory, lead to deficiencies in circulating levels of testosterone, progesterone, and corticosterone. However, there are at least two other sources for cellular cholesterol, de novo synthesis and scavenger receptor class B type I-mediated uptake of HDL cholesteryl ester (CE). In this study, we measured the rates of net cholesterol acquisition by these three pathways in the adrenal, ovary, and testis. In all three organs, the majority (81-98%) of cholesterol acquisition came from the selective uptake of CE from HDL and de novo synthesis. Furthermore, in the npc1(-/-)mouse, the cytosolic storage pool of CE in a tissue such as the adrenal remained constant (approximately 25 mg/g). As a result of these alternative pathways, the plasma concentrations of testosterone (3.5 vs. 2.5 ng/ml), progesterone (8.5 vs. 6.7 ng/ml), and corticosterone (391 vs. 134 ng/ml) were either the same or elevated in the npc1(-/-)mouse, compared with the control animal. Thus, impairment of cholesterol acquisition through the NPC1-dependent, clathrin-coated pit pathway did not limit the availability of cholesterol substrate for steroid hormone synthesis in the steroidogenic cells.

Central organization of androgen-sensitive pathways to the hypothalamic-pituitary-adrenal axis: implications for individual differences in responses to homeostatic threat and predisposition to disease

Despite clear evidence of the potency by which sex steroids operate on the hypothalamic-pituitary-adrenal (HPA) axis and genuine sex differences in disorders related to HPA dysfunction, the biological significance of this remains largely ignored. Stress-induced increases in circulating glucocorticoid levels serve to meet the metabolic demands of homeostatic threat head-on. Thus, the nature of the stress-adrenal axis is to protect the organism. As one develops, matures, and ages, still newer and competing physiological and environmental demands are encountered. These changing constraints are also met by shifts in sex steroid release, placing this class of steroids beyond the traditional realm of reproductive function. Here we focus on the dose-related and glucocorticoid-interactive nature by which testosterone operates on stress-induced HPA activation. This provides an overview on how to exploit these characteristics towards developing an anatomical framework of testosterone's actions in the brain, and expands upon the idea that centrally projecting arginine vasopressin circuits in the brain act to register and couple testosterone's effects on neuroendocrine and behavioural responses to stress. More generally, the work presented here underscores how a dual adrenal and gonadal systems approach assist in unmasking the bases by which individuals resist or succumb to stress.

Testosterone down-regulates ornithine aminotransferase gene and up-regulates arginase II and ornithine decarboxylase genes for polyamines synthesis in the murine kidney

The enzymes ornithine aminotransferase (OAT) and ornithine decarboxylase (ODC) share L-ornithine as a common substrate and arginase II produces this amino acid. In the murine kidney, testosterone induced ODC gene expression and polyamine production, but it is unknown how OAT gene is expressed under androgen treatment. These experiments were designed to study the influence of testosterone on the renal expression of OAT gene. Pharmacological and physiological doses of testosterone were injected into female and castrated male mice. Total RNA and soluble proteins extracted from whole kidneys were analyzed by Northern and Western blots, respectively. The results clearly indicate that pharmacological doses of testosterone simultaneously down-regulated the level of OAT protein and up-regulated the expression of arginase II and ODC genes. Variations of the levels of OAT protein and arginase II mRNA and protein were strongly correlated with testosteronemia. Orchidectomy increased the renal level of OAT protein and decreased that of ODC and arginase II. These effects were reversed by injecting a physiological dose of testosterone into castrated male mice. In conclusion, OAT and ODC genes are inversely regulated by testosterone in the mouse kidney. Consequently, in kidneys of testosterone-treated mice, L-arginine-derived ornithine produced by arginase II might be preferentially used by ODC for putrescine production rather than by OAT. This metabolic fate of L-ornithine was facilitated by decreasing OAT gene expression. In contrast, in female and castrated male mice devoided of testosterone, OAT gene is highly expressed and L-ornithine is converted into L-glutamate.

Localization and differential expression of arginase II in the kidney of male and female mice

Arginase II (AII) has been almost exclusively studied in male mammalian kidneys. Our investigations were conducted to localize AII gene expression in the female mouse kidney, and to analyze the differential expression of AII gene at the transcriptional and translational levels in the kidneys of female and male mice. Total RNAs and soluble proteins extracted from renal zones and whole kidneys were analyzed by Northern and Western blots, respectively. Mitochondrial and cytosolic proteins were analyzed by Western blot. L-[guanidino-14C]arginine hydrolysis by AII was detected in microdissected tubules and the 14CO2 released from [14C]urea hydrolysis was quantified. The results of these experiments showed that: (1) both AII mRNA and protein were highly expressed in the deep cortex and the outer stripe of the outer medulla, (2) urea was produced mainly in the proximal straight tubules (PST), (3) the 38-kDa AII protein was more abundant in the mitochondria than the cytosol, and (4) the renal content of AII mRNA and protein was about three-fold higher in female than in male mice. In conclusion, in both genders, AII gene expression is restricted to the PST and localized into mitochondria. AII gene is differentially expressed in the kidney of female and male mice since higher levels of AII mRNA, protein and activity were observed in the kidneys of the former than those of the latter. Renal AII gene expression was gender-dependent in mice but not in rats. Finally, in the PST of females, L-arginine-derived ornithine may be a precursor for the renal production of L -glutamate and L-glutamine because high levels of AII, ornithine aminotransferase and glutamine synthetase are expressed in this nephron segment.

CAR, Driving into the Future

The nuclear orphan receptor CAR is active in the absence of ligand with the unique capability to be further regulated by activators. A number of these activators, including phenobarbital, do not directly bind to the receptor. Considered a xenobiotic sensing receptor, CAR transcriptionally modifies the expression of genes involved in the metabolism and elimination of xenobiotics and steroids in response to these compounds and other cellular metabolites. Its hepatic expression pattern endows the liver with the ability to protect against not only exogenous but also endogenous insults. The mechanism of CAR activation is complex, involving translocation from the cytoplasm to the nucleus in the presence of activators, followed by further activation steps in the nucleus. Although this mechanism remains under investigation, we have summarized here the cellular signaling pathways elucidated so far and speculate on the mechanism by which CAR activators regulate gene expression through this network.

Elevated steroidogenesis, defective reproductive organs, and infertility in transgenic male mice overexpressing human chorionic gonadotropin

We previously developed a transgenic (TG) mouse model that overexpresses the human chorionic gonadotropin (hCG) beta-subunit under the universal human ubiquitin C promoter, displaying in males a modest 3-fold increase in circulating levels of LH/hCG bioactivity. The males were fertile and presented with a mild reproductive phenotype. To achieve higher levels of hCG, a double TG model was generated by cross-breeding the hCG beta-expressing mice with another TG line harboring a ubiquitin C/common alpha-subunit fusion gene. The double-TG mice expressed excessive levels of dimeric hCG, with 2000-fold elevated circulating LH/hCG bioactivity. These male mice were infertile, primarily due to inability to copulate, and they showed enhanced testicular androgen production despite clear down-regulation of LH/hCG receptors. Their intratesticular inhibin B was unaltered, but serum FSH was markedly reduced. Apparently the chronic hCG hyperstimulation led to focal Leydig cell proliferation/hypertrophy at 6 months of age, but failed to promote testicular tumors. Even though full spermatogenesis occurred in most of the seminiferous tubules, progressive tubule degeneration was apparent as the males grew older. The prostate and seminal vesicles were enlarged by distension of glandular lumina. Functional urethral obstruction was indicated by distension and sperm accumulation in distal vas deferens as well as by dilated urinary bladder and enlarged kidneys. The abnormal function of accessory sex glands and/or lower urinary tract as a consequence of the disturbed sex hormone balance or direct action of hCG may be the main cause of infertility in this model. The present study provides in vivo evidence that exposure of male mice to chronically elevated levels of hCG severely affects their urogenital tract function at multiple sites and causes infertility, but, unlike in LH/hCG overexpressing female mice, it is not tumorigenic.

Progestin receptor immunoreactivity within steroid-responsive vasopressin-immunoreactive cells in the male and female rat brain

Progestin receptor immunoreactivity is found in the same regions of the bed nucleus of stria terminalis (BST) and centromedial amygdala (CMA) as steroid-responsive vasopressin immunoreactive (AVP-ir) cells. To test whether AVP-ir cells express progestin receptors, brains of male rats were stained immunocytochemically for arginine vasopressin as well as progestin receptors. In BST and CMA, over 95% of AVP-ir cells contained progestin receptor immunoreactivity. In contrast, none of the AVP-ir cells in the suprachiasmatic, supraoptic and paraventricular nuclei expressed progestin receptor immunoreactivity. To study whether progestin receptor expression in AVP-ir cells in the BST and CMA is responsive to gonadal steroids, male and female rats were castrated and implanted with either empty capsules or capsules filled with testosterone or oestradiol, respectively. Ten days later, brains were processed for AVP and progestin receptor immunoreactivity. Although there was no effect of hormonal status on the percentage of colocalized cells, the level of progestin receptor immunoreactivity was higher in rats that received gonadal steroids than those that did not. The presence of progestin receptor immunoreactivity in steroid responsive AVP-ir cells, and the responsiveness of this expression to gonadal hormones, is consistent with the possibility that the effects of gonadal steroids on AVP-ir expression in the BST and CMA may be mediated at least in part by progestin receptors.

Functional cross-talk between the hypothalamic-pituitary-gonadal and -adrenal axes

Under normal conditions, the adrenal glucocorticoids, the endproduct of the hypothalamic-pituitary-adrenal (HPA) axis, provide a frontline of defence against threats to homeostasis (i.e. stress). On the other hand, chronic HPA drive and glucocorticoid hypersecretion have been implicated in the pathogenesis of several forms of systemic, neurodegenerative and affective disorders. The HPA axis is subject to gonadal influence, indicated by sex differences in basal and stress HPA function and neuropathologies associated with HPA dysfunction. Functional cross-talk between the gonadal and adrenal axes is due in large part to the interactive effects of sex steroids and glucocorticoids, explaining perhaps why several disease states linked to stress are sex-dependent. Realizing the interactive nature by which the hypothalamic-pituitary-gonadal and HPA systems operate, however, has made it difficult to model how these hormones act in the brain. Manipulation of one endocrine system is not without effects on the other. Simultaneous manipulation and assessment of both endocrine systems can overcome this problem. This dual approach in the male rat reveals that testosterone can act and interact on different aspects of basal and stress HPA function. Basal adrenocorticotropic hormone (ACTH) release is regulated by testosterone-dependent effects on arginine vasopressin synthesis, and corticosterone-dependent effects on corticotropin-releasing hormone (CRH) synthesis in the paraventricular nucleus (PVN) of the hypothalamus. In contrast, testosterone and corticosterone interact on stress-induced ACTH release and drive to the PVN motor neurones. Candidate structures mediating this interaction include several testosterone-sensitive afferents to the HPA axis, including the medial preoptic area, central and medial amygdala and bed nuclei of the stria terminalis. All of these relay homeostatic information and integrate reproductive and social behaviour. Because these modalities are affected by stress in humans, a dual systems approach holds great promise in establishing further links between the neuroendocrinology of stress and the central bases of sex-dependent disorders, including psychiatric, cardiovascular and metabolic disease.

Genotype/age interactions on aggressive behavior in gonadally intact estrogen receptor beta knockout (betaERKO) male mice

Estrogen, as an aromatized metabolite of testosterone, has a facilitatory effect on male aggressive behavior in mice. Two subtypes of estrogen receptors, alpha (ER-alpha) and beta (ER-beta), in the brain are known to bind estrogen. Previous studies revealed that the lack of ER-alpha gene severely reduced the induction of male aggressive behavior. In contrast, mice that lacked the ER-beta gene tended to be more aggressive than wild type (WT) control mice, although the behavioral effects of ER-beta gene disruption were dependent on their social experience. These findings lead us to hypothesize that estrogen may facilitate aggression via ER-alpha whereas it may inhibit aggression via ER-beta. In the present study, we further investigated the role of ER-beta in the regulation of aggressive behavior by examining developmental changes starting at the time of first onset, around the age of puberty. Aggressive behaviors of ER-beta gene knockout (betaERKO) mice were examined in three different age groups, puberty, young-adult, and adult. Each mouse was tested every other day for three times in a resident-intruder paradigm against olfactory bulbectomized intruder mice and their trunk blood was collected for measurements of serum testosterone after the completion of the study. Overall, betaERKO mice were significantly more aggressive than WT. These genotype differences were more pronounced in puberty and young adult age groups, but not apparent in the adult age group, in which betaERKO mice were less aggressive than those in two younger age groups. Serum testosterone levels of betaERKO mice were significantly higher than those of WT mice only in the pubertal age group, but not in young adult (when betaERKO mice were still significantly more aggressive than WT mice) and adult (when no genotype differences in aggression were found) age groups. These results suggest that ER-beta mediated actions of gonadal steroids may more profoundly be involved in the inhibitory regulation of aggressive behavior in pubertal and young adult mice.

Semen quality and hormone levels among radiofrequency heater operators

Approximately 9,000,000 US workers are occupationally exposed to radiofrequency (RF) radiation; over 250,000 operate RF dielectric heaters. Our purpose was to determine whether male RF heater operators experience increased adverse reproductive effects reflected in reduced semen quality or altered hormone levels. We measured incident RF heater radiation exposures and RF-induced foot currents at four companies. For 12 male heater operators and a comparison group of 34 RF-unexposed men, we measured 33 parameters of semen quality and four serum hormones. Despite wide variation in individual exposure levels, near field strengths and induced foot currents did not exceed current standard levels and guidelines. We observed minor semen quality and hormonal differences between the groups, including a slightly higher mean follicle-stimulating hormone level for exposed operators (7.6 vs 5.8 mIU/mL). Further occupational studies of RF-exposed men may be warranted.

Population pharmacokinetic/pharmacodynamic modeling of cetrorelix, a novel LH-RH antagonist, and testosterone in rats and dogs

PURPOSE

Population models for the pharmacokinetic-pharmacodynamic relationship for cetrorelix (CET), a luteinising hormone-releasing hormone (LH-RH) antagonist, and the pharmacodynamic response on testosterone production were investigated in rats and dogs.

METHODS

The plasma concentrations of CET and testosterone were determined after intravenous and subcutaneous injections. The population PK/PD-models were developed using P-PHARM software.

RESULTS

Absolute bioavailability of cetrorelix was 100% in rats and 97% in dogs. In rats, the pharmacokinetics was explained by a two-compartment model with saturable absorption, while a three-compartment model was used in dogs. Testosterone suppression in both species was described by a sigmoid E(max) model with maximum effect (E(max)) considered as total hormonal suppression. The duration of testosterone suppression in rats was longer at higher doses. The population elimination half-lives after iv-dose were 3.0 h in rats and 9.3 h in dogs. Population mean estimates of IC50 were 1.39 and 1.24 ng/ml in rats and dogs, respectively.

CONCLUSIONS

A population pharmacokinetic model was developed to explain the dissolution rate limited absorption from the injection site. The suppression of testosterone could be described by an indirect inhibitory sigmoid E(max) model. In both species 1-2 ng/ml CET in plasma was necessary to suppress testosterone production.

Many LH peaks are needed to physiologically stimulate testosterone secretion: modulation by fasting and NPY

The pulsatile luteinizing hormone (LH) and testosterone secretions were studied during serial blood collections performed at 7-min time intervals in the male rat. In fed rats, a discontinuous pattern of LH secretion was observed. Periods without secretion alternated with active secretory episodes consisting in trains of three to four LH peaks that triggered testosterone secretion usually 1-2 h later. The magnitude of the testosterone response was not correlated with the amplitude of the LH peaks. Isolated, single peaks of LH did not evoke clear testosterone responses. Forty-eight hours after initiation of fasting, testosterone secretion was markedly decreased, but integrated LH secretion was only partly reduced. Chronic infusion of neuropeptide Y (NPY; 18 microgram/day, icv) reduced testosterone secretion to very low levels and abolished pulsatile LH secretion or testosterone response to isolated LH peaks. In conclusion, the stimulation of testosterone secretion by LH necessitates several LH peaks organized in a proper sequence, and the testosterone response is not immediate. Low testosterone secretion in fasting rats appears to result from disappearance of coordinated, multiple LH peaks of sufficient size. Inhibition of the gonadotropic axis achieved by central NPY administration is due to either absence of LH peak "clusters" or occurrence of nonfunctional single LH peaks.

Basal concentrations of various steroids in the nonobese diabetic (NOD) mouse and effect of immobilization stress

The progression of type I diabetes in the NOD mouse is modulated by, among other things, stressful events and steroids. We measured in 2-month-old prediabetic NOD mice various circulating steroids (progesterone, corticosterone, dehydroepiandrosterone, delta4-androstenedione, testosterone, estrone and estradiol) under basal and stressful conditions (1.5h immobilization). Basal progesterone concentrations were low but measurable in randomized cycling NOD females and under the detection limit in NOD males. Immobilization increased progesterone concentrations in both sexes. Serum corticosterone concentrations also increased after immobilization but with the sexual dimorphism normally observed in rodents. Dehydroepiandrosterone concentrations were similar in both sexes and remained unaffected by stress. Testosterone and delta4-androstenedione were drastically reduced after immobilization in NOD males. Serum estrone and estradiol were not found to be statistically different in NOD females and males, but slightly higher to that described in the literature, and immobilization increased estrone concentrations in NOD males. In conclusion, while nonspecific to the NOD mouse, the modulation of circulating corticosteroids, estrogens and androgens induced by environmental factors may be part of the mechanism(s) by which these factors modulate the progression of type I diabetes. The hormonal changes may act in a complex manner at different levels: the immune system, the islet of Langerhans and the other structures involved in glucose homeostasis.

Receptors for anti-müllerian hormone on Leydig cells are responsible for its effects on steroidogenesis and cell differentiation

Strong overexpression of anti-Müllerian hormone (AMH) in transgenic mice leads to incomplete fetal virilization and decreased serum testosterone in the adult. Conversely, AMH-deficient mice exhibit Leydig cell hyperplasia. To probe the mechanism of action of AMH on Leydig cell steroidogenesis, we have studied the expression of mRNA for steroidogenic proteins in vivo and in vitro and performed a morphometric analysis of testicular tissue in mice overexpressing the hormone. We show that overexpression of AMH in male transgenic mice blocks the differentiation of Leydig cell precursors. Expression of steroidogenic protein mRNAs, mainly cytochrome P450 17 alpha-hydroxylase/C17-20 lyase (P450c17), is decreased in transgenic mice overexpressing AMH and in AMH-treated purified Leydig cells. In contrast, transgenic mice in whom the AMH locus has been disrupted show increase expression of P450c17. In vitro, but not in vivo, AMH also decreases the expression of the luteinizing hormone receptor. The effect of AMH is explained by the presence of its receptor on Leydig cells. Our results provide insight into the action of AMH as a negative modulator of Leydig cell differentiation and function.

Citral and testosterone interactions in inducing benign and atypical prostatic hyperplasia in rats

Citral is a monoterpene in wide use as an aromatic supplement in the cosmetics and food industries. Previous studies in our laboratory have shown that cutaneous application of citral on adolescent rats may induce benign prostatic hyperplasia (BPH)-like and even atypical hyperplastic changes in the ventral lobes. In the present study we investigate the possible interactions between citral and serum testosterone levels on the induction of hyperplastic changes in the ventral prostate of adolescent rats. In addition, the study includes a comparative analysis of normal intact rats showing circadian variations of serum testosterone levels and rats in whom this rhythmic pattern was abolished either by excessive supplementation of exogenous androgen or by castration. Our results demonstrate an induction of benign as well as atypical prostatic hyperplasia following citral application. The most severe atypical changes were noted in the citral-treated rats with high serum testosterone levels. Although the mechanism of action of citral is yet unknown, the present results suggest a synergism between citral and testosterone resulting in hyperplastic changes in the rat ventral prostate. In addition, the results reconfirm that serum testosterone levels fluctuate according to a circadian rhythm in intact young and adolescent male rats. The application of citral tends to lower the morning circadian peaks, and the circadian pattern was abolished in orchiectomized rats and in those treated with testosterone implants.

Steroid control of higher brain function and behavior

In higher vertebrates, many behavioral characteristics can be attributed to effects in the central nervous system, in response to gonadal hormones secreted early in development. The lipophilic properties of steroids facilitate their easy passage in free form through the blood-brain barrier. At the cerebral level, the function of many nerve cells is influenced by steroid hormones originating from the periphery (synthesis of gluco-, and mineralo-corticosteroids in the adrenal glands and of sex steroids in the gonads and the placenta from cholesterol). However, the relationship between steroids and cerebral function may need reconsidering in light of the recent discovery of a biosynthetic pathway (independently of peripheral sources) of steroidal compounds ensuring the synthesis of neurosteroids from cholesterol in certain brain cells.

Effects of thyroid hormone on the androgenic expression of KAP gene in mouse kidney

The kidney androgen-regulated protein (KAP) gene exhibits a cell-specific hormonal regulation of its expression in the epithelial cells of proximal tubules of mouse kidney, where T3 is required for constitutive expression in the straight segments and androgens for expression in the convoluted ones. By using different models of hypothyroidism, we demonstrate that maximal androgen-mediated induction of the gene depends on thyroid hormone as well. This constitutes a specific event, since vitamin D3 cannot mimic the effects of T3, albeit their remarkable functional relationship. It is also shown that while congenital hypothyroid hyt/hyt male mice, exposed to maternal T3 in the gestational period, exhibit diminished but existent androgen-dependent cortical responses, mice exposed to goitrogens during gestation and postnatally are unable to express the gene even at postnatal day ninety. Impairment of KAP cortical expression in hypothyroid animals does not correlate with lower levels of androgens or androgen receptor expression.

Boar proacrosin expressed in spermatids of transgenic mice does not reach the acrosome and disrupts spermatogenesis

Transgenic mice that express boar proacrosin were produced to examine mechanisms for targeting hydrolytic enzymes to the acrosome. A 2.3 kb transgene was constructed by ligating the cDNA for boar preproacrosin with the mouse protamine 2 promoter region. Six founder mice that incorporated the transgene were identified by polymerase chain reaction and Southern blot analysis. Northern blots indicated that the two male founders (Ac.2 and Ac.5) and male progeny from three female founders (Ac.3, Ac.4, Ac.6) expressed the transgene mRNA in testis, but not in somatic tissues. In these transgenic animals boar proacrosin was detected by immunohistochemistry in condensing spermatids, but was not localized in the acrosome. This acrosomal targeting defect of the transgene product may result from its delayed expression during the later steps of haploid differentiation. Furthermore, both male founders and all Ac.4 and Ac.6 males were infertile, as determined by multiple matings for at least 2 months. Ac.3 males were either infertile or rarely transmitted the transgene to their offspring. The infertile males mated, produced copulatory plugs, and had seminal vesicle weights and testosterone levels within the normal range. However, they produced significantly fewer spermatozoa and had lower testis weights than controls. Although the mitotic and meiotic phases of spermatogenesis appeared normal by histological criteria, condensing spermatids were missing from most tubules, and multinucleated cells were present in the lumen of seminiferous tubules and in the epididymis. We hypothesize that boar proacrosin which fails to reach the acrosome is activated in these transgenic mice, and that its proteolytic activity disrupts spermatogenesis during spermatid formation.

Pharmacology of novel steroidal inhibitors of cytochrome P450(17) alpha (17 alpha-hydroxylase/C17-20 lyase)

Medical or surgical castration for the treatment of prostatic cancers prevents androgen production by the testes, but not by the adrenals. Inhibition of the key enzyme for androgen biosynthesis, cytochrome P450(17) alpha, could prevent androgen production from both sources. The in vivo effects of 17-(3-pyridyl)androsta-5,16-dien-3 beta-ol (CB7598) and 17-(3-pyridyl)androsta-5,16-dien-3-one (CB7627), novel potent steroidal inhibitors of this enzyme, on WHT mice were compared with those of castration and two clinically active compounds, ketoconazole and flutamide. Flutamide and surgical castration caused significant reductions in the weights of the ventral prostate and seminal vesicles. CB7598, in its 3 beta-O-acetate form (CB7630), and CB7627 caused significant reductions in the weights of the ventral prostate, seminal vesicles, kidneys and testes when administered once daily for 2 weeks. Ketoconazole, given on the same schedule, caused no reductions. Plasma testosterone was reduced to < or = 0.1 nM by CB7630, despite a 3- to 4-fold increase in the plasma level of luteinizing hormone. Adrenal weights were unchanged following treatment with CB7630 or CB7627 but were markedly increased following ketoconazole, indicating no inhibition of corticosterone production by these steroidal compounds. These results indicate that CB7598, CB7630 or CB7627 may be useful in the treatment of hormone-dependent prostatic cancers.

Structure, function, and regulation of androgen-binding protein/sex hormone-binding globulin

Despite over 20 years of research, the functions of ABP and SHBG remain elusive. The major reason for this lack of knowledge has been the unavailability of natural mutants with clinical defects for study. There is strong evidence that these binding proteins do act to modulate the gene regulatory actions of nuclear sex steroid receptors by controlling the availability of androgens and estrogens. In plasma, SHBG controls the metabolic clearance rate of sex steroids. In addition there is strong evidence that they have a much broader function. The identification of plasma membrane receptors in target tissues and the finding of homologous domains in several developmental proteins support other functions. Moreover, other experiments suggest the proteins may actually be hormones or growth factors. These findings are not compatible with a model that has the proteins only regulating free steroid hormone levels. Obviously, much more experimentation will be necessary to reveal the functions of ABP and SHBG. The recent discoveries have offered several clues to their functions and open new routes for study. These experiments, coupled with newly developed techniques, such as gene knockout by homologous recombination, make one optimistic that the functions of these unique proteins will be deciphered in the near future.

Comparison of liver glutathione peroxidase activity and mRNA in female and male mice and rats

1. Female and male adult mouse and rat liver was analyzed for glutathione peroxidase activity, mRNA levels, and other selected liver enzymes. 2. Species and sex differences in liver protein, total RNA and total mRNA were minor. 3. Glutathione peroxidase activity, mRNA levels, and selenium concentration was lower in male rats when compared to female rats, male mice or female mice. 4. Plasma ceruloplasmin activity, but not liver mRNA levels, were lower in mice compared to rats. 5. Cu,Zn-superoxide dismutase activity and mRNA were not greatly influenced by species or sex. 6. Glutathione transferase activity towards 1-chloro-2,4-dinitrobenzene was highest in male mice and equivalent in the other three groups.

Differential lateral septal vasopressin innervation in aggressive and nonaggressive male mice

The vasopressinergic (VP) projection from the bed nucleus of the stria terminalis (BNST) to the lateral septum (LS) is sexually dimorphic and dependent of androgens at adult and neonatal age. We studied the relation between testosterone (T) and VP in male mice, which were genetically selected for their differences in aggression level. Aggressive males, characterized by a short attack latency (SAL), have a higher production capacity of T at adult age compared to males with a long attack latency (LAL). Neonatally, however, a higher T production occurs in the nonaggressive LAL males than in SAL males. In the present study we showed a more dense VP-immunoreactive (VP-ir) innervation in the LS and a higher VP-ir neuron density in the BNST of LAL males as compared to SAL males. The described differences may be the consequence of a differential neonatal androgen effect on the organization of the forebrain vasopressinergic network.

Temporal structure of in vivo adrenal secretory activity estimated by deconvolution analysis

Circadian and ultradian rhythms of plasma cortisol concentrations have been documented under physiological conditions in diverse animal species. Using a novel, biophysical convolution model to remove subject-specific metabolic clearance rates, we have now estimated spontaneous adrenal secretory events in vivo. The latter were characterized by prominent ultradian rhythms of discrete secretory bursts with periodicities averaging 32, 46, 76, and 130 min. These ultradian cortisol secretory rhythms represented a 17- to 240-fold larger fraction of circadian secretory variations than did cortisol concentration rhythms. We conclude that deconvolution analysis can unmask underlying ultradian rhythms in adrenal secretory activity in vivo.

Y chromosome and aggression in strains of laboratory mice

Intermale attack behavior differences in laboratory strains of inbred mice have Y chromosome correlates in a small number of strain comparisons. Moreover, the Y correlates interact with autosomal or pseudoautosomal genes. Recent data on the genetics of the Y do not contradict these conclusions. The discovery of several polymorphic loci of the Y could pave the way for a direct confirmation of Y correlates of attack behavior by linkage detection. The involvement of the Y in this behavior has been put forward. Plasmatic testosterone concentration reactivity of some target organs to exogeneous testosterone appears to be correlated with two independent loci of the Y acting in an additive or interactive manner with autosomal or pseudoautosomal loci. However, the association between testosterone action and attack behavior in males needs further evidence, and in any case this association does not underline linear mechanisms.

Prenatal stress reduces fertility of male offspring in mice, without affecting their adult testosterone levels

The male offspring of mice stressed by crowding during the final third of pregnancy showed reductions in sexual behavior and fertility. When paired with receptive females, their latencies to mount and to achieve intromission and ejaculation were greater than controls, and 30% of them failed to ejaculate in the 100-min test. When housed continuously for 4 days with females, 31% of them failed to impregnate their partners, compared with 4% of controls. The sexual receptivity of the untreated females paired with prenatally stressed males was not affected. Resting testosterone levels of prenatally stressed males did not differ from those of controls, and the pattern of rise and fall of testosterone during a 60-min interaction with a female showed only minor differences. The results suggest a central, rather than peripheral, mediation of the behavioral effects of prenatal stress.

Amplitude modulation of a burstlike mode of cortisol secretion subserves the circadian glucocorticoid rhythm

We have examined the mechanism subserving the in vivo circadian rhythm of cortisol in men. To this end, blood samples were withdrawn at 10-min intervals for 24 h in each of six men to yield well-defined profiles of episodic cortisol release. A novel multiple-parameter deconvolution model was applied to discriminate the number, amplitudes, and durations of all statistically significant underlying cortisol secretory bursts from the plasma hormone concentrations and simultaneously estimate the endogenous half-life of cortisol disappearance in each subject. These experiments disclosed randomly occurring cortisol secretory bursts at a mean frequency of 19 +/- 0.82 events per day (interpulse interval 77 +/- 4.0 min). Secretory bursts exhibited a mean half-duration (duration at half-maximal amplitude) of only 16 +/- 0.61 min indicating that 95% of daily cortisol secretion occurred in 8.2 h. Cortisol secretory burst frequency varied 2.2-fold over 24 h, whereas cortisol secretory burst amplitude varied 6.6-fold. We conclude that the nyctohemeral pattern of cortisol variation in vivo can be accounted for by an amplitude-modulated, random burstlike mode of cortisol secretion without the need to postulate a tonic mode of cortisol release.

The adrenal gland and progesterone stimulates testicular steroidogenesis in the rat in vivo

Administration of pharmacological doses of glucocorticoid to male rats in vivo suppresses adrenal steroidogenesis and inhibits testicular steroidogenesis by inhibiting the anterior pituitary secretion of LH. In contrast, administration of ACTH to these pharmacologically-suppressed rats stimulates the adrenal secretion of progesterone and testicular steroidogenesis. The mechanism by which ACTH increases testicular steroidogenesis is dependent on the presence of the adrenal gland and is reproduced by the administration of progesterone. The conclusion from these data is that the adrenal gland has an important role in generating external signals that modulate the hypothalamic-pituitary-gonadal axis in male rats. The adrenal secretion of glucocorticoid acts as a negative signal to testicular steroidogenesis whereas progesterone acts as a positive signal. The adrenal secretion of progesterone and its conversion to testosterone by steroidogenic enzymes in the cytoplasm of the Leydig cell may provide an alternative pathway for testosterone biosynthesis and may account for the increased plasma testosterone levels during the acute phase of stress and mating.

Developmental changes in lactate dehydrogenase-X activity in young jaundiced male rats

This study was designed to examine the testicular maturation in both jaundiced (jj) and nonjaundiced (Jj) male Gunn rats as indicated by the activity of a testis and sperm-specific enzyme, lactate dehydrogenase-X (LDH-X), and serum testosterone levels. Testicular cytosolic LDH-X activity was determined by oxidation of reduced nicotinamide adenine dinucleotide (NADH). Serum testosterone levels were measured by radioimmunoassay (RIA). Testicular LDH-X activity increased rapidly between 30 and 50 days of age in both Jj and jj Gunn rats. LDH-X activity was significantly lower in the jj Gunn rats at 50 and 60 days of age. Testosterone level was significantly lower in the jj Gunn rats at 50 days of age. LDH-X activity and serum testosterone levels were similar for both genotypes at 180 days of age. The delay of testicular maturation in the jaundiced males seems to be due to lower LDH-X activity and serum testosterone levels.

Gonadal steroid influence upon sexual and aggressive behavior of female rats

The present experiment investigates the activation of aggressive and sexual behaviors by gonadal hormones in female rats of the S3-strain. In the first experiment three doses of testosterone propionate (TP) were chronically injected. In the second experiment effects of TP were compared to those of estradiol benzoate (EB) and methyltrienelone (R1881), a synthetic, unaromatizable androgen. Females of the S3-strain were tested against TP-treated female Wistar rats as opponents, and masculine and feminine sexual responses were assessed in the test for aggression as well as in separate tests with sexually active stimulus animals. The results of the first experiment indicate that TP in all doses, increased aggressive as well as sexual behavior equally, although plasma testosterone levels differed significantly between the groups. In the second experiment, EB significantly decreased overall aggression as compared to control-treatment. TP- and R1881-stimulated fighting, particularly, as the most offensive parameter of aggression, but did not increase overall levels of aggression. Tests for sexual preference in which the choice between a sexually active male or female was given, indicated that TP-treated females stayed near males with longer durations. Scentmarking frequencies, measured in the semiopenfield test, were effectively activated by TP-treatment. EB- and R1881-treatment resulted in intermediate levels of marking behavior.

Influence of photoperiod and gonadal steroids on hibernation in the European hamster

Torpor was monitored daily in adult male and female European hamsters (Cricetus cricetus) induced to hibernate by exposure to a cold environment (6 degrees C). The effect of photoperiodic manipulations or administration of exogenous gonadal steroids was examined in gonadectomized or intact hamsters. 1. Gonadal regression occurred in all short day, but only in some long day, cold-exposed hamsters. Entry into hibernation was not observed until reproductive regression had occurred. Thus, gonadal atrophy appears to be a necessary precondition for hibernation. 2. Castrated hamsters in the short day cold condition showed a significantly greater incidence of torpor than those in the long day cold condition. Hence, photoperiod affected torpor independently of its effect on the gonadal cycle. 3. Testosterone, when administered via silastic capsules at near physiological levels, completely inhibited torpor in gonadectomized male and female hamsters hibernating in the short day cold condition. 4. In ovariectomized females, torpor was unaffected by progesterone treatment, but partially inhibited by estradiol. A greater inhibition of torpor was observed when estradiol-primed females were administered both estradiol and progesterone simultaneously. Thus, the effect of both hormones may be functionally comparable to that of the single testicular hormone. 5. Estradiol inhibited torpor to a greater extent in intact and ovariectomized female hamsters hibernating in long days than those in short days, suggesting an effect of photoperiod on responsiveness to estradiol. These results indicate an inverse relationship between the gonadal and hibernation cycles, and a probable role for gonadal steroids to influence the timing of the hibernation season. However, non-gonadal factors must also be involved in controlling hibernation, since photoperiod affected the incidence of torpor in gonadectomized animals and because hamsters were able to terminate hibernation in the absence of gonadal hormones.

The effect of androgen deprivation on branching morphogenesis in the mouse prostate

Androgen-induced prostatic development encompasses many individual processes such as ductal branching morphogenesis, cellular proliferation, and secretory cytodifferentiation. Previous studies of ductal morphogenesis (Y. Sugimura, G.R. Cunha, and A.A. Donjacour, 1986, Biol. Reprod. 34, 961-971) demonstrated that the majority (approximately 70%) of ductal tips and branchpoints in the mouse prostate is generated before 15 days of age. Since circulating androgen levels are low during this neonatal period, it is possible that ductal branching morphogenesis may not require the continuous presence of androgens. To test this hypothesis mice were castrated within 24 hr of birth, and prostates from these mice were microdissected at various ages from 5 to 120 days of age to assess the number of ductal tips and branchpoints; wet weight and DNA content were also determined. In intact males wet weight and DNA content increased rapidly between 15 and 60 days of age, after most of the prostatic ductal architecture had been laid down. Neonatal castration considerably reduced the number of tips and branchpoints in both the ventral and dorsolateral prostate, yet both lobes still underwent significant branching morphogenesis in the absence of testes. The administration of anti-androgens to neonatal castrates did not suppress ductal branching to any greater extent than did neonatal castration alone. Androgen replacement immediately following neonatal castration resulted in precocious attainment of the adult number of tips and branchpoints, but caused only modest increases in wet weight. In contrast, when androgen replacement was delayed until adulthood, prostatic wet weight increased to normal adult levels, but the number of ductal tips and branchpoints did not. These experiments show that neonatal prostatic ductal morphogenesis is sensitive to, but does not require, chronic androgen stimulation.

Pituitary-testicular reserve in men with low serum testosterone and normal serum luteinizing hormone

Men with low serum testosterone levels who do not have elevated serum LH levels are generally thought to have hypothalamic-pituitary dysfunction. To evaluate this concept, seven men with a combination of low serum testosterone and normal serum LH underwent standard tests of hypothalamic-pituitary-testicular reserve. Pituitary reserve, tested with LHRH, showed exaggerated responses in two subjects, low-normal responses in one subject, and normal responses in the remaining four. Testing of hypothalamic-pituitary reserve with clomiphene showed normal gonadotropin responses in six subjects and blunted response in one (the same subject with the low LHRH response). Direct stimulation with hCG showed normal percentage increases in testosterone but low absolute levels, comparable to responses in patients with Klinefelter's syndrome. However, 17-OH-progresterone responses to hCG were lower in these subjects than in either controls or subjects with Klinefelter's syndrome. During follow-up, one subject developed frank primary testicular failure. It was concluded that men with low serum testosterone but normal serum LH are a heterogeneous group, and this pattern occasionally reflects early primary testicular failure rather than hypothalamic-pituitary dysfunction. Standard tests of pituitary-testicular reserve are generally not useful in defining abnormal hormonal output, although measurement of the 17-OH-progesterone response to hCG may improve their diagnostic utility.

Decreased serum testosterone response to gonadotropin-releasing hormone in male offspring of diabetic female rats

A study was designed to examine the testicular function of male offspring rats produced by diabetic dams. A marked decrease in testosterone response to exogenous administration of gonadotropin-releasing hormone (GnRH) was found in male offspring of female rats made diabetic by administration of streptozotocin during early pregnancy. Control rats responded to GnRH with a marked increase in serum testosterone within 4-h postinjection. Male offspring of diabetic female rats demonstrated an unexpected decrease in serum testosterone in response to GnRH when compared with saline-injected rats. The results suggest that a defect in Leydig cell function may occur in the male offspring of diabetic female rats. However, a decreased release of pituitary LH in response to exogenous GnRH stimulation cannot be excluded as a cause of the lower testosterone values.

Influence of photoperiod, ambient temperature and melatonin on testosterone synthesis and release during reproductive maturation in male deer mice

Four experiments were designed to investigate the influence of photoperiod and other environmental factors on androgen production and reproductive maturation in deer mice. Male prairie deer mice (Peromyscus maniculatus), born in a light/dark cycle of 6L:18D, either remained in this short photoperiod or were switched to a long day regimen of 16L:8D at weaning. In a cross-sectional experiment, the deer mice were killed between 3 and 8 weeks of age for measurement of serum testosterone concentration and reproductive organ weights. In a second experiment, blood was collected from each mouse at weekly intervals between 3 and 9 weeks of age. This repeated measures design was used to reduce the high variability in testosterone values observed in the first experiment. Reproductive organs were weighed at the termination of the experiment. Testosterone concentrations and reproductive organ weights were greater in males reared in the long photoperiod in both experiments. In a third experiment, the animals were housed under five different conditions to test the influence of high ambient temperature and melatonin as well as photoperiod. At 7 weeks of age, they received an injection of hCG or saline. More testosterone was released in deer mice reared in 16L:8D and 27 C than in those reared in short days (6L:18D) or those reared in high ambient temperature (35 C) or those treated with exogenous melatonin. One week later, animals were sacrificed. The single hCG treatment caused significant reversal of the suppression of accessory sex organ weights following melatonin, short days or 35 C temperature. In a fourth experiment, the additive influence of melatonin and 35 C temperature was tested. Animals treated with 35 C or both melatonin and 35 C had lower serum testosterone at 7 weeks of age, released less testosterone after hCG, and had smaller organ weights with or without hCG than long day controls. The influence of melatonin treatment and 35 C temperature appears to be additive for testicular weight and testosterone release after hCG. Thus, the attenuation of reproductive development that accompanied short days, melatonin treatment and high ambient temperature occurred via diminished testosterone secretion, which can be overcome at least in part by gonadotropin treatment.

Urinary excretion of free glucocorticosteroids and testosterone in the Mongolian gerbil (Meriones unguiculatus): effects of long-acting corticotrophin and human gonadotrophin

1. Methods for the quantitative collection of 24-hr urines of small laboratory animals and for the measurement of urinary free glucocorticosteroids and testosterone are described. 2. Urinary glucocorticosteroids and testosterone were determined in 0.1-0.5 ml-aliquots of 1/100 diluted urines after kieselgur mini-column extraction. 3. Excretion of glucocorticosteroids and testosterone in undisturbed Mongolian gerbils was 329 and 13 ng/day, respectively. 4. Administration of long-acting (1-24)ACTH (20 IU/animal) increased glucocorticosteroid and testosterone excretion to about 2000 ng/day (glucocorticosteroids) and to about 30 ng/day (testosterone) over 3 days. 5. In animals injected with 100 IU/animal HCG, testosterone excretion was elevated to about 35-50 ng/day over 3 days. 6. As the results show, the measurement of urinary excretion of free glucocorticosteroids and testosterone is a reliable index of adrenal-gonadal function in the Mongolian gerbil. 7. Furthermore, in small laboratory animals, steroid measurements in 24-hr urines may be superior to determinations in plasma, since amounts of urinary steroid are relatively high and 24-hr urines can be collected over longer time periods without stressing the animals.

Deprivation and repletion of androgen in vivo modifies triacylglycerol synthesis by rat hepatocytes

Given the same quantity of fatty acid, livers from male rats esterify less fatty acid and secrete less triacylglycerol in very-low-density lipoprotein than do livers from female animals. To elucidate the role of testosterone in maintenance of this male pattern, conversion of [1-14C]oleic acid into triacylglycerol was assessed in vitro by rat hepatocytes (male) following gonadectomy and replacement with testosterone. Following castration, incorporation of fatty acid into triacylglycerol was increased. In contrast, esterification of exogenous fatty acid into phospholipid, cholesteryl esters, and diacylglycerol was unchanged. Treatment with testosterone (75 micrograms/day) reduced incorporation of exogenous fatty acid into triacylglycerol. Higher doses of testosterone (200 or 100 micrograms/day) modified the effect, such that inhibition was observed only at low oleate (0.5 mM) concentrations. At higher substrate concentrations (1.0-2.0 mM) the inhibitory effect was no longer observed. Further, a similar dose-dependent effect of testosterone was observed following in vivo treatment of castrate females with testosterone. These data support the concept of a regulatory role of testosterone in hepatic triacylglycerol synthesis. These findings also demonstrate a biphasic effect of testosterone, an effect that is dependent not only upon the dose of testosterone administered, but also on the concentration of fatty acid to which the hepatocyte is exposed in vitro.

Lack of effects of polychlorinated biphenyls on testosterone synthesis in mice

Male mice were exposed to two different preparations of PCBs. The pure congener 2,2',4,4',5,5'-hexachlorobiphenyl (6-CB) was given at daily doses of 4, 20, and 40 mg/kg b.wt. during the perinatal or pubertal period. A technical mixture of PCB (Clophen A50) was administered during puberty at daily doses of 8, 40, 80, 120, and 160 mg/kg b.wt. Treatments were, in the different experiments, carried out every second or third day for three to five weeks. Treatment during puberty was started when the mice were 5 weeks old. The perinatal exposure was started on day 13 of gestation and ended on day 24 post partum. There were no significant differences in the plasma levels of testosterone between the treated mice and the controls after any of the treatments, but there was an increase in the relative testes weights for the animals treated perinatally. No influence on the biosynthesis of testosterone in the testicular interstitial cells in vitro could be demonstrated.