Enhance Testosterone Production Research Articles

Effect ofTypha capensis(Rohrb.)N.E.Br. rhizome extract F1 fraction on cell viability, apoptosis induction and testosterone production in TM3-Leydig cells

Typha capensis (Rohrb.)N.E.Br. (bulrush) is used by traditional healers in Southern Africa to treat male reproductive problems. This study aimed at investigating the effects of T.capensis on TM3-Leydig cells. T.capensis rhizome crude extract obtained from autumn, winter, spring and summer harvest was fractionated using HPLC into four fractions, and TM3-Leydig cells were incubated with different concentrations of the F1 fraction (0.01, 0.02, 0.1, 1, 10 and 100μg/ml) for 24, 48 and 96hr respectively. The following parameters were evaluated: cell morphology, viability (MTT assay), testosterone production (testosterone ELISA test), apoptosis (Annexin V-Cy3 binding) and DNA fragmentation (TUNEL assay). Results revealed that the summer harvest obtained the highest amount of extract. The F1 fraction of all harvests was the most effective. This fraction significantly enhanced testosterone production in TM3 cells in a dose-dependent manner with maximum effect at 0.1μg/ml. At higher concentrations, lower testosterone production was observed. Cell viability including apoptosis was not affected at concentrations used by the traditional healers to treat patients. This study shows that T.capensis enhanced testosterone production and might be useful to treat male infertility and ageing male problems.

Effect of Kaempferia parviflora extract and its polymethoxyflavonoid components on testosterone production in mouse testis-derived tumour cells

Low testosterone is associated with late-onset hypogonadism, age-related disease, type 2 diabetes, and cardiovascular disease. In this study, we investigated the effects of Kaempferia parviflora extract and two of its components, 5,7-dimethoxyflavone and 5-hydroxy-3,7,3′,4′-tetramethoxyflavone, on testosterone production in mouse testis-derived tumour cells I-10. K. parviflora fractions containing 5,7-dimethoxyflavone elicited testosterone production in these cells, as did nobiletin, a polymethoxyflavonoid found in citrus species, but not K. parviflora, which was used as a comparative control. Furthermore, we found that these compounds enhanced testosterone production via cyclic AMP (cAMP)/cAMP response element binding protein signalling. In particular, the compounds inhibited activation of phosphodiesterase and thereby increased production of cAMP. These findings support the possibility that K. parviflora extract, 5,7-dimethoxyflavone, and nobiletin may mitigate age-related disease and hypogonadism by enhancing testosterone production.

Geranylgeraniol enhances testosterone production via the cAMP/protein kinase A pathway in testis-derived I-10 tumor cells

Testosterone levels in men decrease with age; this decline has been linked to various diseases and can shorten life expectancy. Geranylgeraniol (GGOH) is an isoprenoid found in plants that plays an important role in several biological processes; however, its role in steroidogenesis is unknown. Here, we report that GGOH enhances the production of testosterone and its precursor progesterone in testis-derived I-10 tumor cells. GGOH induced protein kinase A (PKA) activity and increased cAMP levels and was found to regulate cAMP/PKA signaling by activating adenylate cyclase without altering phosphodiesterase activity. GGOH also stimulated mRNA and protein levels of steroidogenic acute regulatory protein, a downstream effector in the cAMP/PKA pathway. These results demonstrate that GGOH enhances steroidogenesis in testis-derived cells by modulating cAMP/PKA signaling. Our findings have potential applications for the development of therapeutics that increase testosterone levels in aging men.

Osteocalcin Induces Growth Hormone/Insulin-Like Growth Factor-1 System by Promoting Testosterone Synthesis in Male Mice

Osteocalcin has been shown to enhance testosterone production in men. In the present study, we investigated the effects of osteocalcin on testosterone and on induction of the growth hormone/insulin-like growth factor-1 axis. Osteocalcin injection stimulated growth, which could be inhibited by castration. In addition, osteocalcin induced testosterone secretion in testes both in vivo and in vitro. Using real-time polymerase chain reaction and Western blotting, we showed that growth hormone expression was significantly increased in the pituitary after osteocalcin injection (p<0.05). Growth hormone expression in CLU401 mouse pituitary cells was also significantly stimulated (p<0.05) by osteocalcin-induced MA-10 cells. Osteocalcin injection also promoted hepatic expression of growth hormone receptor and insulin-like growth factor-1 (p<0.05), as demonstrated by real-time polymerase chain reaction and Western blotting. Similarly, osteocalcin-induced MA-10 cells promoted growth hormone receptor and insulin-like growth factor-1 expression in NCTC1469 cells. These results suggest that the growth-stimulating activities of osteocalcin are mediated by testicular testosterone secretion, and thus provide valuable information regarding the regulatory effects of osteocalcin expression on the growth hormone/insulin-like growth factor-1 axis via reproductive activities.

Serum osteocalcin is associated with improved metabolic state via adiponectin in females versus testosterone in males. Gender specific nature of the bone–energy homeostasis axis

ObjectiveThe osteoblast-derived protein osteocalcin (OCN) is known to be involved in glucose metabolism by increasing adiponectin secretion from adipocytes. Recently, OCN was also found to enhance testosterone production in mouse testes, suggesting that OCN effects on energy metabolism may be mediated through testosterone. Our aim was to assess a possible gender difference in the metabolic effect of OCN in humans. MethodsWe included 135 women and 155 men exhibiting changes in glucose tolerance in our study. Oral and intravenous glucose tolerance tests (OGTT and IVGTT, respectively) and a hyperinsulinemic normoglycemic clamp were performed. For clamp indices, whole body (M1) and muscle (M2) glucose uptake values were used. Leptin, adiponectin serum lipid, lipoprotein, total serum OCN and testosterone levels, and body composition were determined. ResultsHigher OCN values were associated with improving metabolic state in both genders. Adiponectin and OCN correlated significantly only in females (r=+0.254, p=0.0029), while in men, testosterone and OCN values showed a significant positive correlation (r=+0.243, p=0.0023), independent of age, BMI, HbA1c and body composition. In women, adiponectin was confirmed by feature selection analysis as being an independent determinant of OCN, in addition to age and three of the IVGTT glucose values. In men, besides M1, BMI, M2, leptin, body fat percent, and the 90-minute OGTT glucose reading testosterone, but not adiponectin were identified as independent contributors for OCN. ConclusionWe confirmed the ‘classic’ adiponectin-mediated insulin-sensitising effect of OCN only in females. In men, a testosterone-mediated OCN metabolic effect is more likely.

Osteocalcin is not a strong determinant of serum testosterone and sperm count in men from infertile couples

Osteocalcin (OC) - released by osteoblasts and known as a marker of bone turnover - has been suggested to influence male fertility in murine models by enhancing testosterone production and sperm count. Results from clinical studies are scarce, however. The aim of this cross-sectional study was to investigate the proposed association of OC, undercarboxylated osteocalcin (ucOC) or carboxylated osteocalcin (cOC) with testosterone and sperm count in a cohort of 159 young male adults from infertile couples. Semen analysis was performed. Testosterone, free testosterone, LH, OC and ucOC were measured in serum samples after an overnight fast. cOC and OC correlated weakly but significantly with testosterone (OC: r = 0.165, p = 0.040, cOC: r = 0.193, p = 0.017), but not after adjusting for age and body mass index (BMI) or waist-hip ratio (WHR). %ucOC (ucOC levels expressed as percentage of total OC) correlated inversely with LH (r = -0.184, p = 0.023) and remained significant after the same adjustment. No significant correlations were observed between OC, cOC, ucOC, %ucOC and sperm count, semen volume and number of vital spermatozoa. In binary logistic regression analyses, none of the parameters of OC were predictors of oligozoospermia after adjusting for age and BMI or WHR. The weak association between %ucOC and LH has marginal clinical importance because of the lack of associations of parameters of OC with testosterone and sperm count. The current data thus cannot support the notion that OC is associated with male fertility in young men from infertile couples.

Endocrine Actions of Osteocalcin

Osteocalcin is the most abundant noncollagenous protein of bone matrix. Once transcribed, this protein undergoes posttranslational modifications within osteoblastic cells before its secretion, including the carboxylation of three glutamic residues in glutamic acid, which is essential for hydroxyapatite binding and deposition in the extracellular matrix of bone. Recent provocative data from experimental observations in mice showed that the circulating undercarboxylated fraction of osteocalcin increases insulin secretion and sensitivity, lowers blood glucose, and decreases visceral fat in both genders, while it enhances testosterone production by the testes in males. Moreover, both total and undercarboxylated osteocalcins increase following physical activity with potential positive effects on glucose tolerance. Despite that these evidences have been only in part confirmed in humans, further prospective investigations are needed to definitively establish the endocrine role of osteocalcin both in the general population and cohorts of patients with diabetes or other metabolic disorders.

Menaquinone-4 enhances testosterone production in rats and testis-derived tumor cells

BackgroundVitamin K is essential for the posttranslational modification of various Gla proteins. Although it is widespread in several organs, including the testis, the function of vitamin K in these organs is not well characterized. In this study, we investigated the function of vitamin K in the testis and analyzed its role in steroidogenesis.MethodsEight-week-old male Wistar rats were fed a diet supplemented with menaquinone-4 (MK-4, 75 mg/kg diet), one of the predominant K2 vitamins present in the testis, for 5 weeks. In vivo testosterone levels of the rats' plasma and testes were measured by enzyme-linked immunosorbent assay, and in vitro testosterone levels of testis-derived tumor cells (I-10 cells) maintained in Ham's F-10 medium with 10% fetal bovine serum were measured following treatment with MK-4 (0 to 100 μM) at several time points. Testosterone and cellular protein levels were analyzed with respect to their effects on steroidogenesis.ResultsTestosterone levels in the plasma and testes of MK-4-fed rats were significantly increased compared to those of control rats, with no obvious differences in plasma luteinizing hormone levels. Secreted testosterone levels from I-10 cells were elevated by MK-4, but not by vitamin K1, in a dose-dependent manner independent of cAMP treatment. Western blot analysis revealed that expression of CYP11A, the rate-limiting enzyme in steroidogenesis, and phosphorylation levels of protein kinase A (PKA) and the cAMP response element-binding protein were all stimulated by the presence of MK-4. Enhancement of testosterone production was inhibited by H89, a specific inhibitor of PKA, but not by warfarin, an inhibitor of γ-glutamylcarboxylation.ConclusionsMK-4 stimulates testosterone production in rats and testis-derived tumor cells via activation of PKA. MK-4 may be involved in steroidogenesis in the testis, and its supplementation could reverse the downregulation of testosterone production in elders.

Endocrine Regulation of Male Fertility by the Skeleton

Interactions between bone and the reproductive system have until now been thought to be limited to the regulation of bone remodeling by the gonads. We now show that, in males, bone acts as a regulator of fertility. Using coculture assays, we demonstrate that osteoblasts are able to induce testosterone production by the testes, though they fail to influence estrogen production by the ovaries. Analyses of cell-specific loss- and gain-of-function models reveal that the osteoblast-derived hormone osteocalcin performs this endocrine function. By binding to a G protein-coupled receptor expressed in the Leydig cells of the testes, osteocalcin regulates in a CREB-dependent manner the expression of enzymes that is required for testosterone synthesis, promoting germ cell survival. This study expands the physiological repertoire of osteocalcin and provides the first evidence that the skeleton is an endocrine regulator of reproduction.

Testosterone synthesized in cultured human SZ95 sebocytes derives mainly from dehydroepiandrosterone

Human sebaceous gland possesses all the steroidogenic enzymes required for androgen synthesis. It remains unclear whether the testosterone produced in situ mainly derives from circulating dehydroepiandrosterone (DHEA) or from de novo synthesis utilizing serum cholesterol. Using testosterone radioimmunoassay, we found that testosterone was barely detectable in the supernatant of cultured human SZ95 sebocytes when cholesterol was added alone, indicating a low basal expression of steroidogenic acute regulatory protein (StAR) in SZ95 cells. Human chorionic gonadotropin and fibroblast growth factor-9 were as potent as forskolin in activating StAR to enhance testosterone production, while interleukin-1 beta, dexamethasone, insulin and insulin-like growth factor-1 showed no stimulatory effect. A two-fold increase of testosterone production was observed in supplementation of DHEA as compared to pregnenolone, progesterone or 17 alpha-hydroxyprogesterone. Based on our findings, testosterone synthesized in cultured sebocytes derived mainly from DHEA and inhibition of 3beta-hydroxysteroid dehydrogenase and 17beta-hydroxysteroid dehydrogenase may be a new target of androgen suppression for acne treatment.

Effects of hypoxia on testosterone release in rat Leydig cells

The aim of this study was to explore the effect and action mechanisms of intermittent hypoxia on the production of testosterone both in vivo and in vitro. Male rats were housed in a hypoxic chamber (12% O(2) + 88% N(2), 1.5 l/ml) 8 h/day for 4 days. Normoxic rats were used as control. In an in vivo experiment, hypoxic and normoxic rats were euthanized and the blood samples collected. In the in vitro experiment, the enzymatically dispersed rat Leydig cells were prepared and challenged with forskolin (an adenylyl cyclase activator, 10(-4) M), 8-Br-cAMP (a membrane-permeable analog of cAMP, 10(-4) M), hCG (0.05 IU), the precursors of the biosynthesis testosterone, including 25-OH-C (10(-5) M), pregnenolone (10(-7) M), progesterone (10(-7) M), 17-OH-progesterone (10(-7) M), and androstendione (10(-7)-10(-5) M), nifedipine (L-type Ca(2+) channel blocker, 10(-6)-10(-4) M), nimodipine (L-type Ca(2+) channel blocker, 10(-5) M), tetrandrine (L-type Ca(2+) channel blocker, 10(-5) M), and NAADP (calcium-signaling messenger causing release of calcium from intracellular stores, 10(-6)-10(-4) M). The concentrations of testosterone in plasma and medium were measured by radioimmunoassay. The level of plasma testosterone in hypoxic rats was higher than that in normoxic rats. Enhanced testosterone production was observed in rat Leydig cells treated with hCG, 8-Br-cAMP, or forskolin in both normoxic and hypoxic conditions. Intermittent hypoxia resulted in a further increase of testosterone production in response to the testosterone precursors. The activity of 17β-hydroxysteroid dehydrogenase was stimulated by the treatment of intermittent hypoxia in vitro. The intermittent hypoxia-induced higher production of testosterone was accompanied with the influx of calcium via L-type calcium channel and the increase of intracellular calcium via the mechanism of calcium mobilization. These results suggested that the intermittent hypoxia stimulated the secretion of testosterone at least in part via stimulatory actions on the activities of adenylyl cyclase, cAMP, L-type calcium channel, and steroidogenic enzymes.

Modulation of Leydig cell testosterone production by secretory products of macrophages.

Unstimulated macrophages from testes inhibited the production of testosterone by Leydig cells from adult, but not immature, Sprague-Dawley rats (significant after 48 h). Similar results were observed with unstimulated macrophage-conditioned media, suggesting that the observed effect was mediated by one or more secretory products. None of these substances was interleukin-1, since macrophage supernatants tested negative in an interleukin-1 alpha and interleukin-1 beta sensitive, thymocyte assay. Interleukin-6 was detected by a B cell proliferation assay. After stimulation by LPS, testicular macrophages enhanced testosterone production by Leydig cells from adult and immature rats. This enhancement was dose-dependent and required low concentrations (but over 2.5%) of conditioned media. Interleukin-1 and interleukin-6 activities were detected in LPS-stimulated macrophage supernatants. Supernatants of LPS-stimulated, human monocytes had similar effects on Leydig cells. They were rich in interleukin-1, interleukin-1 receptor antagonist and interleukin-6. The present study suggests that, in adult rats, testicular macrophages modulate Leydig cell steroidogenesis by secretory products whose secretion depends on the physiological state of macrophages. The factor or factors responsible for stimulation are not species-specific. The effect cannot be accounted for by variations in the concentration of the above mentioned interleukins in macrophage supernatants.

In vitro study of the effects of khat ( Catha edulis Forsk) extract on isolated mouse interstitial cells

Isolated mouse interstitial cells were incubated with different concentrations of khat ( Catha edulis) extract (0.06 mg/ml, 0.6 mg/ml, 6 mg/ml, 30 mg/ml and 60 mg/ml) and cell viability as well as testosterone concentration measured at 30 min intervals over a 3 h incubation period. High concentrations of khat extract (30 mg/ml and 60 mg/ml) significantly inhibited testosterone production while low concentrations (0.06 mg/ml, 0.6 mg/ml and 6 mg/ml) significantly stimulated ( P < 0.05) testosterone production by mouse interstitial cells. Similarly, at concentrations of 30 mg/ml and 60 mg/ml, there was a significant decrease in interstitial cell viability, whereas at 0.06 mg/ml, 0.6 mg/ml and 6 mg/ml there was no significant decrease. There was only a weak correlation ( r = 0.39) between testosterone production and viable interstitial cells. We postulate that khat extract at high concentrations may cause reproductive function impairment in the user but at low concentrations, may enhance testosterone production with accompanying effects on reproductive functions in male mice.

Involvement of D-Asp in P450 aromatase activity and estrogen receptors in boar testis

Mammalian testis contains D-aspartic acid (D-Asp), which enhances testosterone production. D-Asp, on other hand, also stimulates 17beta-estradiol synthesis in the ovary of some lower vertebrates. We studied boar testis in order to determine if D-Asp intervenes in 17beta-estradiol synthesis in the testis of those mammals which produce significant amounts of estrogens as well as testosterone. The boar testis contains D-Asp (40 +/- 3.6 nmol/g tissue) which, according to immunohistological techniques, is localized mainly in Leydig cells, and, to a lesser extent, in sustentacular (Sertoli), peritubular and some germ cells. The enzyme P450aromatase is present in Leydig cells and few germ cells. In vitro experiments showed that the addition of D-Asp to testicular tissue extracts induced a significant increase of aromatase activity, as evaluated by testosterone conversion into 17beta-estradiol. The enzyme's K(m) was not affected by D-Asp (about 25 nM in both control and D-Asp added tests). On the basis of these results we suggest that, as in the ovary, D-Asp is involved in the local control of aromatase activity of boar testis and, therefore, it intervenes in the 17beta-estradiol production. In the testis, the D-Asp targets are presumably the Leydig cells, which having also a nuclear estrogen receptor are, in turn, one of the putative targets of the 17beta-estradiol that they produce (autocrine effect).

Effects of Basella alba and Hibiscus macranthus extracts on testosterone production of adult rat and bull Ley dig cells

To determine the androgenic effects of Basella alba and Hibiscus macranthus extracts in the rat and the bull, and to develop a novel in vitro test system using Leydig cells from bull testes. The effect of methanol extracts from both plants on testosterone production in isolated Leydig cells from the rat and the bull was analyzed using 125I-radioimmunoassay (125I-RIA). Rat Leydig cells were obtained by common methods, whereas a novel technique was used to purify Leydig cells from bull testes. Bull testes from the slaughter house were a cheap source of pure Leydig cells. In culture, these cells produced testosterone for 5-6 days, which can be stimulated by human chorionic gonadotrophin (hCG). Basella alba extracts significantly enhanced testosterone production in bull and rat Leydig cells in a concentration-dependent manner. Hibiscus macranthus showed no androgenic effect but was shown to inhibit testosterone production at higher concentrations. Leydig cells purified from bull testes can be used as an alternative tool in experimental animal research. Certain fractions of Basella alba extract demonstrated androgenic potential whereas Hibiscus macranthus extracts did not.

Effect of Troglitazone on the Excess Testosterone and LH Secretion in Thyroidectomized, Insulin-Resistant, Type 2 Diabetic Goto–Kakizaki Rats

Our previous study suggested that hypothyroidism in Goto-Kakizaki (GK) rats with insulin resistance and type 2 diabetes elevates their serum testosterone and luteinizing hormone (LH) levels and ovarian LH receptor messenger RNA (mRNA) expression. The present study assessed the effects of troglitazone (Tro), an insulin-sensitizing agent, on these hypothyroidism-induced hormonal changes in GK rats. GK and normal (Wistar strain) female rats were thyroidectomized (Tx) and then injected with 5 IU of equine chorionic gonadotropin (eCG) for 5 d starting 1 wk after thyroidectomy (the control groups). In the test groups, Tx GK and Wistar rats were injected with both eCG and Tro (100 mg kg-1) po for 5 d. Tro treatment had no effect on the elevated LH serum levels in eCG-treated Tx GK rats but suppressed their enhanced serum testosterone levels as well as significantly decreasing their LH receptor mRNA expression. Tro lowered testosterone and LH receptor mRNA levels in cultured theca cells. These results indicate that Tro lowers the elevated testosterone secretion and ovarian LH receptor mRNA expression that is induced in GK rats by Tx and gonadotropin treatment, which suggests that insulin resistance may be involved in enhancing testosterone production and LH receptor expression in the ovary.

Regulation of thyroid hormones on the production of testosterone in rats

The effects of a thyroidectomy and thyroxine (T4) replacement on the spontaneous and human chorionic gonadotropin (hCG)-stimulated secretion of testosterone and the production of adenosine 3',5'-cyclic monophosphate (cAMP) in rat testes were studied. Thyroidectomy decreased the basal levels of plasma luteinizing hormone (LH) and testosterone, which delayed the maximal response of testosterone to gonadotropin-releasing hormone (GnRH) and hCG in male rats. T4 replacement in thyroparathyroidectomized (Tx) rats restored the concentrations of plasma LH and testosterone to euthyroid levels. Thyroidectomy decreased the basal release of hypothalamic GnRH, pituitary LH, and testicular testosterone as well as the LH response to GnRH and testosterone response to hCG in vitro. T4 replacement in Tx rats restored the in vitro release of GnRH, GnRH-stimulated LH release as well as hCG-stimulated testosterone release. Administration of T4 in vitro restored the release of testosterone by rat testicular interstitial cells (TICs). The increase of testosterone release in response to forskolin and androstenedione was less in TICs from Tx rats than in that from sham Tx rats. Administration of nifedipine in vitro resulted in a decrease of testosterone release by TICs from sham Tx but not from Tx rats. The basal level of cAMP in TICs was decreased by thyroidectomy. The increased accumulation of cAMP in TICs following administration of forskolin was eliminated in Tx rats. T4 replacement in Tx restored the testosterone response to forskolin. But the testosterone response to androstenedione and the cAMP response to forskolin in TICs was not restored by T4 in Tx rats. These results suggest that the inhibitory effect of a thyroidectomy on the production of testosterone in rat TICs is in part due to: 1) the decreased basal secretion of pituitary LH and its response to GnRH; 2) the decreased response of TICs to gonadotropin; and 3) the diminished production of cAMP, influx of calcium, and activity of 17beta-HSD. T4 may enhance testosterone production by acting directly at the testicular interstitial cells of Tx rats.

Transcriptional regulation of the lutropin/human choriogonadotropin receptor and three enzymes of steroidogenesis by growth factors in cultured pig Leydig cells.

Recent data have shown that Leydig-cell-specific functions, and therefore steroidogenic capacity, can be regulated by lutropin/human choriogonadotropin collectively termed gonadotropin and by several growth factors that are produced by and act within the testis. However, the molecular mechanisms by which these factors regulate Leydig cells are not understood. In the present study, we have investigated the effects of basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), insulin-like growth factor I (IGF-I) and transforming growth factor beta (TGF-beta) on mRNA for the gonadotropin receptor and three steroidogenic enzymes: cytochrome P-450scc, cytochrome P-450 17 alpha-hydroxylase/C17-20 lyase (17 alpha-hydroxylase), and 3 beta-hydroxysteroid dehydrogenase. IGF-1, which can enhance testosterone production, increased gonadotropin-receptor density after an increase in receptor mRNA levels, and it increased the level of mRNA for cytochrome P-450scc and 17 alpha-hydrolyase. Micromolar concentrations of insulin had similar effects to those of IGF-I. Moreover, the three factors that decreased testosterone production (EGF, bFGF and TGF beta 1) decreased gonadotropin receptor density, receptor mRNA levels and the mRNA levels for 17 alpha-hydroxylase. The potential effects of these growth factors on the transcription on the gonadotropin genes for the receptor and these three steroidogenic enzymes were measured by means of nuclear run-on assays. We demonstrated that the long-term inhibitory (EGF, bFGF, TGF beta 1) or stimulatory (IGF-I) effects of these growth factors are primarily due to a variation in the transcription rates of genes for the gonadotropin receptor, cytochrome P-450scc and 17 alpha-hydroxylase. Moreover, since previous studies have shown than some of these growth factors are expressed within the testis, they may play a physiological role in the regulation of differentiated testicular functions.

Evidence for Germ Cell Control of Sertoli Cell Function in Three Models of Germ Cell Depletion in Adult Rat

In order to clarify the role of germ cells in the regulation of Sertoli cell secretions, three experimental models of germ cell depletion were used: hypodactyl rat mutation (testis weight [TW]: 55% less than controls), in utero busulfan treatment (TW: 88% less than controls), and neonatal experimental cryptorchidism (TW: 72% less than controls). The aim of this work was to compare the numbers of Leydig and Sertoli cells and the production of germ cells in each experimental model to the in vitro secretions of Leydig and Sertoli cells in conditioned media and to the hormonal serum profiles of the same animal in vivo. In the three models, serum levels of hypophyseal and testosterone hormones were significantly increased and decreased, respectively. In the absence of germ cells, the total length of seminiferous tubules, the total numbers of Sertoli and Leydig cells, and the daily production of germ cells were significantly diminished. The addition of both control and damaged seminiferous tubule culture media (STM: media conditioned by 10 cm of seminiferous tubules) to 10(6) control or damaged Leydig cells led to a further increase of testosterone production after ovine LH stimulation. However, expressed per Sertoli cell, testosterone production by control Leydig cells was reduced by addition of damaged STM as compared to addition of control STM, and similarly, the addition of control STM to damaged Leydig cells enhanced testosterone production more than did the addition of damaged STM. Secretions of transferrin per Sertoli cell in STM were reduced as compared to controls by the absence of germ cells but to a lesser extent than was production of spermatocytes and of spermatids. In conclusion, secretions by Sertoli cells of the paracrine factor involved in the control of testosterone production by Leydig cells and of transferrin are modified by germ cells.

Amplified nocturnal luteinizing hormone (LH) secretory burst frequency with selective attenuation of pulsatile (but not basal) testosterone secretion in healthy aged men: possible Leydig cell desensitization to endogenous LH signaling--a clinical research center study.

The specific mechanisms underlying the relative hypogonadism of aging remain to be elucidated fully. We used frequent venous sampling (every 2.5 min), sensitive and specific LH and testosterone assays, and deconvolution analysis of the endocrine time series to delineate the differences between healthy young (n = 10, age 21-34 yr) and aged (n = 8, age 62-74 yr) men in the nocturnal secretion of LH and testosterone and their half-lives. We found that elderly men vs. young men had more frequent bursts of LH secretion (1.4 vs. 0.9/h, P = 0.003), less testosterone secreted per testosterone secretory burst (9.2 vs. 17.0 nmol/L, P = 0.021), and less testosterone secreted per hour (10.7 vs. 25.0 nmol/L.h, P = 0.05). As the frequency of nocturnal LH secretory bursts increased, the frequency of testosterone bursts decreased (r = -0.746, P = 0.034). We conclude that healthy aging is associated with diminished nocturnal testosterone production attributable to 1) a decrement in the mass of testosterone released per burst and 2) an inadequate response by the pituitary gland to enhance testosterone production via an accelerated LH secretory pulse frequency. We speculate that this may reflect a partial desensitization of Leydig cells to LH.