Effect of the absence of neonatal testosterone imprinting on the activity of the microsomal enzyme system and on the dexamethasone binding of the thymus in adulthood

Healthy and neonatally castrated male rats were treated with testosterone twice perinatally, while other groups were treated with testosterone also in adulthood or received testosterone only in adulthood. Castration resulted in a moderate (but in some instances significant) decrease of PSMO (polysubstrate monooxygenase) level measured in adulthood. The decrease could partially be compensated by perinatal testosterone treatment. Further testosterone treatment administered in adulthood did not result in further alteration when compared either with the controls or with the neonatally treated animals. However, since in the controls the second testosterone treatment (following the neonatal one), had a decreasing effect, therefore the testosterone treatment administered in adulthood was responsible for the disappearance of the difference between the castrated animals and the controls treated both perinatally and in adulthood. On the basis of these findings it seems likely that the perinatal presence of testosterone plays a major role in the development of enzymatic imprinting and thus, in securing the capability of the liver to split testosterone in adulthood. Since testosterone influences the glycocorticoid receptors of the thymus (presumably by its overlapping effect), so the amount of free glycocorticoid receptors is always higher in the animals castrated neonatally than in the controls. Conversely, neonatal testosterone treatment somewhat increases the number of receptors detectable in adulthood.     

The effects of the administration of testosterone propionate alone or with phenobarbitone and of testosterone metabolites to neonatal female rats

The effects of graded doses of testosterone propionate administered to female rats on Day 4 of postnatal life have been determined. The incidence of failure of ovulation as adults was related to the dose. With increasing dosage over the range 1–100 μg no significant evidence of a progressive decrease in immunoassayable luteinizing hormone concentration in the plasma or anterior pituitary was obtained. The reported protective action of sodium phenobarbitone when administered with testosterone propionate could not be confirmed. Single injections of 100 μg of testosterone, dihydrotestosterone, 5 α-androstanediol, or a combination of the two latter compounds had no masculinizing effect. When the 17-β propionate derivatives of these compounds were administered at the same dose level only testosterone propionate had a masculinizing effect.     

Testosterone action on erythropoiesis does not require its aromatization to estrogen: Insights from the testosterone and estrogen treatment of two aromatase-deficient men

Androgens act on erythropoiesis, but the relative role of testosterone (T) and estradiol (E₂) on erythropoietic parameters in men is a poorly investigated issue. In order to evaluate separately the effects on erythropoiesis of high-dose T administration alone and of physiological dose of E₂ administration alone two adult men with aromatase deficiency were assessed before and during each treatment. Blood cell count, hemoglobin (Hb), hematocrit (Hct), erythrocyte mean cell volume (MCV), erythrocyte mean corpuscular hemoglobin (MCH), erythrocyte mean corpuscular hemoglobin concentration (MCHC), serum ferritin, iron and total iron-binding capacity (TIBC), serum erythropoietin, serum total testosterone and estradiol were evaluated. Hb, Hct and red cell count rose during testosterone treatment, consistently with the increase in circulating testosterone, but failed to increase during estradiol treatment. A decrease in Hb, Hct and red cell count was recorded in one of the two subjects during estradiol treatment, with a concomitant decrease in serum testosterone. Circulating T alone is capable of and sufficient to influence erythropoiesis, especially at supraphysiological dosage, while circulating E₂ have not the same effect on erythropoietic parameters, suggesting the hypothesis that the erythropoietic changes induced by androgens are not mediated via its aromatization to estrogens.     

Role of testosterone levels and of hypophysis in the HCG-induced modifications of the 7 alpha-hydroxylation and 5 alpha-reduction processes in incubated rat testes

The role of a direct or a hypophysis-mediated influence of increased testosterone levels in the effects of a long-term high-dose HCG administration (10 IU/day) upon the 7 alpha-hydroxylation and 5 alpha-reduction activities of incubated testes of mature rats was investigated. Administration of high doses of HCG to hypophysectomized rats resulted in the same metabolic changes as in normal rats, namely, a large decrease in the 7 alpha-hydroxylation and an increase in the 5 alpha-reduction processes. Administration of testosterone-propionate (0.2 mg and 20 mg/day) for several days to hypophysectomized rats and to normal rats receiving and substitutive dose of 1 IU HCG/day, did not modify the testicular metabolization pattern. These findings indicate that the decrease in testicular 7 alpha-hydroxylation activity induced by long-term administration of high doses of HCG is probably not mediated by the hypophysis nor by the extracellular testosterone levels.     

Intratesticular distribution of testosterone in rats and the relationship to the concentrations of a peptide that stimulates testosterone secretion

Methods have been established and validated for quantitative assessment of the distribution of testosterone in the testis, by measurement of testosterone concentrations in whole testis, in isolated seminiferous tubules and in testicular interstitial fluid. These measurements were made in individual rats injected 2-40 h previously with saline (0.9% NaCl) or a potent antiserum to ovine LH. Testosterone concentrations in interstitial fluid and seminiferous tubules were closely correlated (r = +0.98; n = 60) and their relationship was log linear over a 200-fold range. However, although the concentrations of testosterone in interstitial fluid and seminiferous tubules decreased progressively with time after LH antiserum injection, this decrease was far more pronounced for interstitial fluid. In association with this change there was a significant increase in the amounts of a locally-produced factor in interstitial fluid which stimulates basal and hCG-stimulated testosterone production by isolated purified Leydig cells. This increase was reversed by injection of hCG but not by peripheral injection of a dose (20 mg) of testosterone propionate which restored normal intratesticular concentrations of testosterone. It is concluded that the tubular 'conservation' of testosterone, which occurs as interstitial fluid levels of this steroid decrease, may be a consequence of restricted diffusion of testosterone out of the tubules, but is also associated with increased amounts of a peptide stimulator of testosterone production.     

The influence of testosterone in the brain of the male rat on levels of serotonin (5-HT) and hydroxyindole-acetic acid (5-HIAA)

There were two groups of rats: one was injected with testosterone propionate (10 mg/kg) every 7 days starting from weaning (23 days old); the other group had gonadectomy on the same day. The levels of 5-HT and 5-HIAA were measured by spectrofluorometry. The concentrations of 5-HT in the diencephalon of the testosterone propionate injected rats decreased significantly at 45 days, tending to become reestablished at 60 days; the rest of the brain followed the same pattern, but was less pronounced. The concentrations of 5-HIAA in the diencephalon and the rest of the brain decrease throughout postnatal development, although the differences are not significant. The castrated rats showed a marked increase at 45 days and later decreased at 60 days without recovering their initial values, in both brain areas. 5-HIAA concentrations were similar to those found in the injected animals. These facts can have various interpretations: early modifications in the brain, feed-back regulation mechanisms at the level of the hypothalamus, decrease in the release of the amine or reduction of its catabolism.     

Effets de l’activité sportive sur les androgènes endogènes

Heavy physical activity, below exhaustion and with a mean duration of less than 2 hours, induces an approximately 50% increase in testosterone serum levels within 10 to 30 minutes. Testosterone drop to baseline levels within 2 hours after cessation of physical activity. However when efforts are too heavy, with too much duration (more than 3 hours) or repetition, a mean 50% decrease in testosterone serum levels is observed. A similar drop is also observed during corticoid treatment or heavy stress such as surgical general anesthesia or acute or chroric diseases. The initial rise in testosterone is too fast to be explained by an increased stimulation of testicle by LH. A more likely explanation is a vascular change leading to an increased testicular blood stream and a decrease in liver clearance. The secondary drop in testosterone serum levels is likely related to cortisol effect on LH receptors of the Leydig cells and also on LH pulses. Men regularly practising a well scheduled physical activity have mean testosterone levels higher than men of the same age not involved in sport. Men exposed too frequently to exhausting physical activity may experience prolonged phase of hypogonadism similar to those observed recently in female athletes.     

Changes in the testicular binding of luteinizing hormone and plasma testosterone concentrations in the Djungarian hamster subjected to different photoperiods and temperatures and effects of long-term testosterone treatment on the binding

The effects of artificial photoperiod, temperature, and long-term testosterone treatment on testicular luteinizing hormone (LH) binding were studied in adult male Djungarian hamsters. In hamsters transferred to long-day (LD; 16 hr light, 8 hr dark) photoperiod 8 weeks after adaptation in short-day (SD; 8 hr light, 16 hr dark) photoperiod of 25 degrees C, testicular growth was associated with an increase in the total LH binding per two testes and a decrease in LH binding per unit testicular weight. Plasma testosterone levels reached a peak 47 days after transfer to LD and tended to decrease thereafter, while the testes continued growing. In contrast, when hamsters reared under LD conditions at 25 degrees C for 12 weeks were transferred to SD, testicular regression was associated with a decrease in plasma testosterone and the total LH binding per two testes and an increase in LH binding per unit testicular weight. A significant decrease in LH binding per unit weight compared to SD controls was observed in those hamsters exposed to SD with continuous testosterone treatment. The testosterone treatment tended to induce decrease in the total LH binding. Scatchard plot analyses of the binding suggested that changes in LH binding were due to changes in the number of binding sites. When sexually mature male hamsters were subjected for 8 weeks to two different ambient temperatures (7 degrees C and 25 degrees C) and photoperiods (LD and SD), the difference between the two temperature groups was statistically not significant regarding the weights of testes, epididymides, and prostates; plasma testosterone levels; and LH binding in either LD or SD group. These results suggest that photoperiod is a more important environmental factor than temperature for the regulation of testicular activity and LH receptors and that testosterone reduces the number of LH receptors per unit testicular weight in adult male Djungarian hamsters.     

Effect of uni- and bilateral cryptorchidism on testicular inhibin and testosterone secretion in rats

The effect of uni- and bilateral cryptorchidism on testicular inhibin and testosterone secretion and their relationships to gonadotropins were studied in rats. Mature Wistar male rats weighing approximately 300 g were made either uni- or bilaterally cryptorchid. Testicular inhibin and testosterone content and plasma levels of LH and FSH were examined 2 weeks later. A similar remarkable decrease in testicular inhibin content was found in uni- and bilaterally cryptorchid testes. On the other hand, the testicular testosterone content was significantly decreased only in unilaterally cryptorchid testis with an inverse increase in the contralateral testis. Plasma testosterone levels were normal and plasma LH and FSH increased significantly in both of the cryptorchid groups. These results showed that cryptorchidism impairs both Sertoli and Leydig cell functions. While testosterone production was compensated by increased LH for 2 weeks, neither inhibin secretion nor storage changed in cryptorchid or contralateral testes during the same period.     

Counteraction of testosterone-induced suppression of the pituitary-ovarian axis in rats by flutamide.

Daily administration of 100 micrograms of testosterone to unilaterally ovariectomized rats for 18 days caused a significant decrease in compensatory ovarian hypertrophy. The number of corpora lutea was markedly reduced and many cystic follicles were noticeable. Administration of graded doses (0.5, 1 and 3 mg daily) of flutamide over the same period did not cause any significant change in the weight and histology of the ovary in untreated unilaterally ovariectomized animals. However, treatment with the same doses of flutamide prevented the changes observed in the reamining ovary of testosterone-treated animals.     

The role of the hypophysis and the hypophyseal hormone prolactin in maintenance of the sexual specificity of the metabolism of testosterone and 5-alpha-dihydrotestosterone in rat liver slices]

Hypophysectomy of rats 55 days after birth causes profound changes in the sexually differentiated liver metabolism of testosterone and 5alpha-dihydrotestosterone, which were studied when the rats were 80 days old. 1. Metabolism of testosterone after hypophysectomy: The turnover of testosterone decreased significantly to the same level in both sexes. The effect was especially marked in the female, which normally has a high turnover of this compound. The sexual differences in the patterns of metabolites were also lost, owing to the following changes: In the male, the high level of metabolites of the 3beta-hydroxy-5alpha-androstane type falls to the low level found in the female controls. The low level of 4-androstene-3,17-dione in the female increases to the high level found in the male controls. The concentrations of testosterone increase and those of the metabolites of the 3-oxo- and 3alpha-hydroxy-5alpha-androstane decrease to values that are significantly much higher or lower, respectively, than the normal values found in the control animals. 2. Metabolism of 5alpha-dihydrotestosterone after hypophysectomy: In comparison with the controls, the turnover of this substrate is significantly decreased by the same factor in both sexes; thus the difference between the sexes persists. In the pattern of metabolites, the sexual differences are still apparent, but less marked. The levels of metabolites show two opposing changes: a significant increase in the concentration of 3beta-hydroxy metabolites, and a significant decrease in the concentration of 3alpha-hydroxy metabolites; although the activity of the microsomal 3alpha-hydroxysteroid dehydrogenase increases by a factor of 3 - 4 in both sexes after hypophysectomy[1]. This discrepancy indicates a compartmentalization of androgen metabolism in the liver cell, in which delta4-5alpha- and 3beta-hydrogenation occur on the membranes of the endoplasmic reticulum, whereas 3alpha-hydrogenation occurs in the cytosol. 3. Action of prolactin on the metabolism of testosterone in hypophysectomized animals: Prolactin (125 mug twice daily from the 70th to the 79th day of life) causes a significant acceleration of the delta4-5alpha-hydrogenation, which is recognized as a significant increase in the concentrations of 5alpha-androstane metabolites; the 3beta-hydroxy compounds in both sexes reach the normal level of male control animals. The significant increase in the concentration of 3alpha-hydroxy compounds is accompanied by a partial reestablishment of the sexual differences. The sex differences in androgen turnover and metabolite pattern are subject to a hypophyseal regulation, which is separate from the gonadotropic partial function. The hydroxylation activity of the liver, measured as the production of C19O3-steroids, is not significantly affected by hypophysectomy or by treatment with prolactin.     

Decrease of mu opioid receptors in the brain and in the hypothalamus of the aged male rat

Experiments have been designed in order to analyze whether the binding capability of mu opioid receptors in the brain of the male rat is modified by age. In a first experiment, the number of receptors (Bmax) and the constant of affinity (Ka) for the mu ligand 3H-dihydromorphine (3H-DHM) have been measured in the whole brain of male rats of 2, 15 and 22 months of age. In a second experiment the Bmax and the Ka for 3H-DHM have been evaluated in the hypothalamus of male rats of 2 and 22 months of age. In this experiment it was also investigated whether the administration of exogenous testosterone modifies the number and/or the affinity of the hypothalamic mu receptors. Serum levels of LH, FSH, prolactin and testosterone have been measured by specific RIAs. The results obtained show that: serum testosterone levels are significantly decreased in aged rats, while serum LH and FSH show only a small decline; serum prolactin is higher in old than in young animals; the number of mu receptors in the whole brain of 15 and 22 month old animals and in the hypothalamus of 22 month old rats is significantly lower than in the same tissues of young animals; the administration to old animals of testosterone, in doses able to bring back towards normal serum levels of testosterone, induces a decrease of LH and FSH, but has no effect on serum prolactin titers. Testosterone administration does not modify the number of hypothalamic mu opioid receptors, indicating that the decline of brain mu receptors in old animals is not the consequence of the physiological decline of testosterone secretion; in no instance the Ka for the mu ligand is significantly affected.     

Effect of immobilization stress on the gonadotropic function of the hypophysis in male hamadryas baboons (Papio hamadryas)

The plasma levels of luteinizing hormone (LH) and testosterone were studied in intact and castrated male baboons exposed to 2- and 10-hour periods of immobilization. Presented data have shown that immobilization stress induced a marked decrease in LH concentration both in intact and castrated monkeys. Changes in LH concentration positively correlated with plasma levels of testosterone only during the experimental procedures. During three days after immobilization there was a sharp dissociation in the dynamics of testosterone levels remained low and LH returned to normal values. We can suggest that it is not absolute LH level that is responsible for the changes in testosterone secretion during the immobilization stress.     

Déficit Androgénique Lié à l’Age

In contrast with the abrupt cessation of ovarian function at menopause in women, alteration of testicular functions in aging males is partial and progressive. Several cross-sectional studies have demonstrated an age-related decrease of testosterone levels in men. This decrease has also been observed when only men in good health are included in such studies. This age-related decline of testosterone levels has been recently confirmed by a longitudinal study including a large number of subjects. The progressive decline begins early, from the late thirties, and continues at a constant rate throughout the subject’s lifetime. Since SHBG increases with age, free testosterone and non-SHBG-bound testosterone (referred to as bioavailable testosterone) decrease more markedly than total testosterone. As variations of SHBG levels (mainly a decrease in obese and/or insulin-resistant subjects) are often encountered in clinical practice and as it is difficult to reliably measure free testosterone, bioavailable testosterone appears to be the better index to diagnose androgen deficiency in the aging male. Elevation of basal LH levels, decrease of hCG-induced testosterone levels and reduction of Leydig cell number demonstrate the testicular origin of hypogonadism. However, gonadotropic function is also relatively altered with aging. As a result of this alteration of gonadotropic function, LH level is not a reliable index of hypogonadism in the aging male. None of the androgen-dependent functions that are altered with aging, i.e. libido, erectile function, sense of well-being, muscle mass, muscle strength, fat mass, bone mass, etc., are exclusively controlled by androgens. In clinical practice, the indication for androgen replacement therapy must therefore be based on a combination of clinical symptoms and a reduction of bioavailable testosterone below a certain cut-off value, indicating “significant” hypogonadism.     

Behavioural and hormonal responses to capture stress in the male red-sided garter snake, Thamnophis sirtalis parietalis

We measured the behavioural and hormonal responses to capture stress in male red-sided garter snakes. Four hours of capture stress resulted in no suppression of mating behaviour relative to control individuals. In contrast, the same stress resulted in a significant increase in plasma levels of corticosterone and a significant decrease in plasma levels of testosterone. There was a significant negative correlation between plasma levels of corticosterone and testosterone in both control and capture-stress groups, suggesting that the increase in corticosterone directly drives the decrease in testosterone. While there was no relation between body size and initial plasma levels of the two steroids, longer individuals had a significantly greater increase in corticosterone following capture stress than did shorter individuals. Snakes display indeterminate growth, suggesting that older individuals have decreased sensitivity to negative feedback in the hypothalamic-pituitary-adrenal axis and thus hypersecrete glucocorticoids. These results suggest that male red-sided garter snakes have uncoupled their behavioural stress response from their hormonal stress response to maximize reproductive opportunities. Copyright 2000 The Association for the Study of Animal Behaviour.     

The opioid agonist ethylketocyclazocine reverts the rapid, non-genomic effects of membrane testosterone receptors in the human prostate LNCaP cell line

Neuropeptides influence cancer cell replication and growth. Opioid peptides, and opiergic neurons are found in the prostate gland, and they are proposed to exert a role in tumor regulation, influencing cancer cell growth, as opioid agonists inhibit cell growth in several systems, including the human prostate cancer cell line LNCaP. In the same cell line, the existence of membrane testosterone receptors was recently reported, which increase, in a non-genomic manner, the secretion of PSA, and modify actin cytoskeleton dynamics, through the signaling cascade FAK-->PI-3 kinase-->Cdc42/Rac1. In the present work, we present data supporting that the general opioid agonist Ethylketocyclazocine (EKC) decreases testosterone-BSA (a non-internalizable testosterone analog) induced PSA secretion. Furthermore, we report that this opioid affects this non-genomic testosterone action, by modifying the distribution of the actin cytoskeleton in the cells, disrupting the above signaling cascade. In addition, after long (>24 h) incubation, opioids decrease the number of membrane testosterone receptors, and reverse their effect on the signaling molecules. In conclusion, our results provide some new insights of a possible action of opioids in prostate cancer control by interfering with the action and the expression of membrane testosterone receptors and signaling.     

The influence of age and testosterone on the ribosomal population in the m. levator ani and a thigh muscle of the rat

Summary The influence of age, castration, and subsequent testosterone treatment on the population of (poly)ribosomes in rat skeletal muscle fibers was studied, using a procedure which clearly differentiates ribonucleoprotein particles from glycogen granules. The m. levator ani, known to be highly reactive to testosterone, was compared with a thigh muscle.The effect of increasing age is about the same in both muscles: the concentration of intermyofibrillar ribosomes decreases, in contrast to the ribosomal abundance in the paranuclear cones of sarcoplasm, which remains approximately constant. Castration and testosterone treatment do not affect the ribosomal concentration in the thigh muscle, but in the m. levator ani the following effects were observed. Castration, performed at six weeks, elicits a marked decrease of the paranuclear ribosomes, but the intermyofibrillar concentration does not noticeably differ from the intact controls. Testosterone, administered at three months following orchidectomy, causes a rapid rise in the paranuclear population. The concentration of the intermyofibrillar ribosomes shows a transient increase. Very early, the concentration of glycogen granules is augmented also, both in between and within the myofibrils. These observations are related to quantitative changes of the contractile system reported previously. It is emphasized that the effects discussed highly depend on the age of orchidectomy.With the technical assistance of Tineke J. Hoogenboezem.     

Neither testosterone levels nor aggression decrease when the male Mongolian gerbil (Meriones unguiculatus) displays paternal behavior

The first studies that correlated mammalian paternal behavior and testosterone levels indicated that the concentration of this steroid hormone decreases when males exhibit paternal care. However, recent studies have also shown that testosterone levels do not decrease when males display paternal behavior. In this study, we measured testosterone levels in plasma throughout the reproductive cycle of the Mongolian gerbil. Testosterone concentrations were correlated with paternal care as well as aggression. We also examined whether there is a trade-off between paternal behavior and aggression in this mammal. Our results show that Mongolian gerbil testosterone levels do not decrease when the males give paternal care. Likewise, male Mongolian gerbils exhibit high levels of aggression while displaying paternal behavior, indicating that there is no trade-off between aggression and paternal behavior. More studies are needed to determine whether testosterone is involved in the regulation of paternal behavior in this rodent.     

Distribution, composition and image analysis of plasma lipoproteins in steroid-treated calves

Six 8-day-old female calves were treated with a subcutaneous implant of 200 mg testosterone + 20 mg estradiol-17 beta. Thirty-five days following implantation, plasma lipoproteins were compared to those in control calves of the same age. The LDL exhibited a slight change in protein and lipid concentrations and no change in particle size. The effects of steroid therapy on HDL and particularly on the lighter density HDL were characterized by a reduction of densities associated with a decrease in protein content, and by a rise in lipids and an increase in particle size. The changes in HDL composition but not in LDL alterations were consistent with those associated with sexual maturation described previously. Although testosterone is the predominant component of our combined preparation, the effects of our treatment on young female calves is not consistent with the data reported for human lipoproteinemia. The high levels of urinary estradiol in treated calves suggest that these effects result more likely from the aromatization of the injected testosterone.     

Female choice and the benefits of mate guarding by male mallards

Pair formation and breeding in many species of waterfowl are separated both temporally and spatially. Most studies of female choice in this group have focused on male characteristics at the time of pairing, with less attention given to how mate choice affects breeding season outcomes. In this study I compared pairing success, male plasma testosterone level and mate-guarding ability of male mallards, Anas platyrhynchos, in two experiments. In the first experiment females and males were group housed with equal sex ratios, thus allowing all of these males to pair. At the same time, an equal number of males was housed in groups without access to females and remained unpaired. In this experiment testosterone levels of paired and unpaired males during autumn (baseline) and spring (breeding) did not differ, indicating that the process of pair formation and breeding does not cause elevated spring testosterone levels in males. However, testosterone did temporarily decrease in paired males during the winter (pair formation) season. In the second experiment groups were male biased, allowing only half of the males to pair. Here paired males had significantly higher testosterone levels than unpaired males during the breeding season, but not during the preceding autumn. Together the results of these experiments indicate that successful pair formation predicts but does not alter male testosterone level during the breeding season. I also found that females paired to males with high levels of testosterone were missing fewer feathers due to forced copulation attempts by nonmates, suggesting that females may choose males based on their mate-guarding abilities. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.