Regulatory cytokine expression and interstitial fluid formation in the normal and inflamed rat testis are under leydig cell control

Leydig cells have been implicated in several inflammation-related responses of the testis. Specifically, these cells produce the proinflammatory cytokines interleukin-1 (IL-1) and IL-6, stimulate macrophage recruitment, and promote interstitial fluid formation. In addition, the immunoregulatory cytokines macrophage migration inhibitory factor (MIF), transforming growth factor-beta1 (TGFbeta1), and interferon-gamma (IFNgamma) are constitutively expressed by testicular cells, including the Leydig cells. In the present study, the contribution of the Leydig cell to testicular inflammatory responses was examined in adult male rats treated with the Leydig cell-specific toxin, ethane dimethane sulfonate (EDS). Intratesticular testosterone levels were modulated by subcutaneous testosterone implants. After 10 days, animals received an injection of lipopolysaccharide (LPS) to induce an inflammatory response, or saline alone, and were killed 3 hours later. Both depletion of Leydig cells by EDS and LPS treatment caused a decrease in collected testicular interstitial fluid to about 35% of control levels, but the effects were not additive. Maintenance of intratesticular testosterone reversed the interstitial fluid decline following EDS treatment and partially prevented the LPS-induced effect. MIF, TGFbeta1, and IFNgamma were expressed in both the normal and inflamed testis at similar levels. In contrast, EDS treatment caused a significant decline in expression of all 3 cytokines, which was prevented by the testosterone implants. These data indicate that 1) expression of TGFbeta1, MIF, and IFNgamma in the testis is not dependent on the presence of intact Leydig cells but is under direct testosterone control and 2) the decline in testicular interstitial fluid during inflammation involves the Leydig cells, acting via both androgens and nonandrogenic secretions. These data provide further support for a significant role for the Leydig cell in modulating the testicular response to inflammation.     

大鼠睾丸Leydig细胞的培养和鉴定

目的:研究体外培养大鼠睾丸Leyd ig细胞的有效方法。方法:原代培养大鼠睾丸Leyd ig细胞,用4 U/m l人绒毛膜促性腺激素(hCG)作用细胞,对照组未用hCG,放射免疫法测定培养液中睾酮浓度,3β羟类固醇脱氢酶(3β-HSD)免疫组化染色观察睾丸Leyd ig细胞形态和生物学特性。结果:培养细胞成分均一、增殖旺盛、分化率高。接种72 h后大鼠睾丸Leyd ig细胞纯度达95%。接种后24 h内,hCG刺激组较对照组睾酮分泌量明显提高(P<0.05)。结论:体外培养的睾丸Leyd ig细胞可分泌高浓度的睾酮;睾丸Leyd ig细胞的纯化和培养方法的建立,可为中老年男性雄激素部分缺乏综合征睾酮替代治疗的基础和临床研究提供一条可行的思路。     

Direct and indirect effects of murine interleukin-2, gamma interferon, and tumor necrosis factor on testosterone synthesis in mouse Leydig cells.

It was recently observed that treatment of patients with a high dosage of human interleukin (IL-2) resulted in suppression of plasma concentrations of testosterone. A murine model was developed to assess the direct and indirect effects of murine IL-2 and the secondarily released cytokines, gamma interferon (INF gamma), and tumor necrosis factor (TNF alpha), on testosterone production in isolated Leydig cells. Pretreatment for 24 hours with IL-2 (100 to 500 IU/ml) or INF gamma (100 to 1000 IU/ml) significantly decreased testosterone production in response to luteinizing hormone (LH; P < 0.02 and 0.005, respectively). The combinations of INF gamma with either TNF alpha or IL-2 produced enhanced suppressive effects on Leydig cell testosterone production. Steroidogenic precursors (22-hydroxycholesterol, 17 alpha-hydroxypregnenolone, and dehydroepiandrosterone) restored testosterone secretion to control levels after preincubation with INF gamma or TNF alpha. In contrast, the inhibition of testosterone synthesis produced by either IL-2 or INF gamma plus TNF alpha could be reversed by 17 alpha-hydroxypregnenolone and dehydroepiandrosterone, but not by 22-hydroxycholesterol (P < 0.01). Dibutyryl cyclic adenosine monophosphate was also ineffective in reversing the inhibitory effects of these cytokines on synthesis. Although IL-2 directly inhibited synthesis in isolated Leydig cells, it stimulated testosterone production (P < 0.005) in minced murine testes. This suggests that IL-2 releases regulatory factors from other cells that were able to overcome the direct inhibitory effect of IL-2. This stimulatory effect was not caused by INF gamma and TNF alpha because INF gamma alone or with TNF alpha inhibited (P < 0.005) testosterone production in minced testes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regulation of spermatogenesis by paracrine／autocrine testicular factors

Spermatogenesis is a complex process regulated by endocrine and testicular paracrine/autocrine factors.Gonadotropins are involved in the regulation of several testicular paracrine factors, mainly of the IL-1 family and testicular hormones. Testicular cytokines and growth factors (such as IL-1, IL-6, TNF, IFN-T, LIF and SCF) were shown to affect both the germ cell proliferation and the Leydig and Sertoli cells functions and secretion. Cytokines and growth factors are produced by immune cells and in the interstitial and seminiferous tubular compartments by various testicular cells, including Sertoli, Leydig, peritubular cells, spermatogonia, differentiated spermatogonia and even spermatozoa. Corresponding cytokine and growth factor receptors were demonstrated on some of the testicular cells. These cytokines also control the secretion of the gonadotropins and testosterone in the testis. Under pathological conditions the levels of pro-inflammatory cytokines are increased and negatively affected spermatogenesis. Thus,the expression levels and the mechanisms involved in the regulation of testicular paracrine/autocrine factors should be considered in future therapeutic strategies for male infertility. (Asian J Androl 2004 Sep; 6: 259-268)     

成人睾丸间质细胞的培养和鉴定

目的寻求一种有效的体外分离、纯化成人睾丸间质细胞的方法。方法利用4个梯度(60%、34%、26%、21%)的Percoll液分离、纯化成人睾丸间质细胞。对分离的细胞进行细胞学观察、锥虫蓝染色、3β羟基类固醇脱氢酶(3βHSD)染色、分泌睾酮能力和绒毛膜促性腺激素(hCG)对分离睾丸间质细胞的作用等检测。结果通过该方法能够获得高纯度(>90%)的成人睾丸间质细胞,并通过上述实验检测证实分离、纯化的睾丸间质细胞有良好的分泌睾酮能力。结论采用该方法对成人睾丸间质细胞进行初步的分离和纯化是简单有效的。     

Testicular steroidogenesis in X/X sex-reversed mice

The sex-reversed X/X Sxr mouse is phenotypically male but lacks germ cells. This provides the opportunity to examine Leydig cell function in the absence of a normal germinal epithelium and without experimental manipulation of the testis. Serum testosterone was lower in Sxr males compared to normal (X/Y) males but there was no significant difference in intratesticular testosterone levels. Serum immunoactive and bioactive luteinizing hormone levels were not significantly different between the two groups. Injection of human chorionic gonadotrophin (hCG) increased intratesticular testosterone in Sxr males more than in normal males although there was no difference in serum testosterone levels. These differences in circulating and intratesticular testosterone levels may be related to reduced blood flow through the Sxr testis. Both basal and hCG-stimulated androgen production by whole testes in vitro were not significantly different between normal and Sxr males. Androgen production per Leydig cell, however, was significantly reduced in cells from Sxr males; this difference was apparent under basal conditions and following stimulation with hCG, dibutyryl cyclic AMP, 22R-hydroxycholesterol or pregnenolone. Results show that in the absence of a normal germinal epithelium there is a decrease in the steroidogenic capacity of the Leydig cells although steroidogenesis by the whole testis is not impaired significantly.     

Leydig cell cooperation in vitro: evidence for communication between adult rat Leydig cells

In short-term incubations (32 C, 3 h) of purified adult rat Leydig cells, increasing the density from 5000 to 50,000 cells/16 mm diameter culture well caused a significant increase in human chorionic gonadotropin (hCG)-stimulated testosterone secretion/cell. Density-dependent stimulation was also observed under basal conditions and in the presence of dibutyryl cyclic adenosine monophosphate, luteinizing hormone-releasing hormone, or 22-hydroxy cholesterol. In contrast, increasing the incubation density of purified Leydig cells by addition of other testicular cells had no effect on basal or hCG-stimulated testosterone secretion. hCG-stimulated testosterone secretion by Leydig cells incubated at low density was also increased by addition of Leydig cell-conditioned medium. This stimulatory activity was removed by charcoal extraction and by ultrafiltration (approximately 30 kDa cut-off). The data indicate that Leydig cells cooperate by secretion of low molecular weight, cell-specific stimulatory factors that support Leydig cell steroidogenesis in vitro, and may also play a role in regulating Leydig cell function in vivo.     

Characterization of insulin binding and comparative action of insulin and insulin-like growth factor I on purified Leydig cells from the adult rat

Insulin binding and insulin action were characterized in adult rat Leydig cells, purified on discontinuous Percoll gradients. Binding of [125I]-porcine insulin was found to be dependent on time, temperature, cell concentration and Leydig cell specific gravity. Competition relative to porcine insulin (100) was as follows: insulin-like growth factor I (IGF-I) : less than 1; proinsulin : 5; guinea-pig insulin : 2; hCG, ovine prolactin and bovine GH : 0. High and low affinity binding sites for insulin were identified on purified Leydig cells with Ka values of 1.2 X 10(9) and 0.3 X 10(8) M-1, with 10,300 and 34,000 binding sites per cells, respectively. Using primary cultures of Leydig cells in serum-free medium, the action of insulin on steroidogenesis was studied and compared with IGF-I action. Insulin and IGF-I used at 1-35 nM enhanced basal testosterone production in a dose-dependent manner; the effect was significant 4 h after administration. Insulin or IGF-I also potentiated the effect of hCG on steroidogenesis during short-term incubation (4 h). Insulin was shown to improve hCG responsiveness without modifying sensitivity to hCG. Moreover, neither cell number nor hCG-binding was altered by insulin, IGF-I or a combination of the two. Concomitant treatment with insulin and IGF-I at half-maximal and maximally effective doses, in the presence or absence of hCG, indicated that the two factors synergized in the stimulation of testosterone production via a common saturable mechanism.     

Differential patterns of inhibin secretion in response to gonadotrophin stimulation in normal men

Inhibin B is produced by the testis, and its constituent alpha and beta B subunits have been localized immunohistochemically to Leydig as well as Sertoli cells in both rodent and human testes. Whether Leydig cells contribute to circulating inhibin B concentrations, however, is uncertain. We have investigated this by selectively stimulating Leydig and Sertoli cells with hCG and FSH, respectively. The study was a randomized crossover trial, investigating responses to 225 IU recombinant FSH or 3000 IU hCG administered s/c 4-6 weeks apart. Ten normal men were recruited to participate. Blood was taken twice before treatment and after 8, 24, 48, 72 and 96 h. Serum was assayed for FSH, LH and testosterone by radioimmunoassay (RIA); inhibin B and pro-alpha C inhibin forms by ELISA. Administration of hCG, but not FSH, caused a rapid increase in blood testosterone levels, which reached a maximum after 72 h (22.2 +/- 2.7-50.1 +/- 4.5 nmol/L, p < 0.001). Inhibin B concentrations in blood were unchanged following either treatment. Conversely, pro-alpha C concentrations increased following both treatments. FSH administration resulted in a gradual increase in pro-alpha C concentrations (369 +/- 18 pg/mL pre-treatment to 453 +/- 33 pg/mL after 96 h, p=0.013). Administration of hCG resulted in a more rapid response, with pro-alpha C concentrations rising from 384 +/- 23 pg/mL pre-treatment to a peak at 48 h of 535 +/- 45 pg/mL (p=0.007). This response was more rapid than that of testosterone. These results demonstrate that adult human Leydig, as well as Sertoli, cells secrete inhibin alpha subunit in response to gonadotrophin stimulation but provide no evidence for the secretion of inhibin B from Leydig cells. The lack of change in inhibin B secretion in response to FSH suggests that more prolonged or intense stimulation of Sertoli cells may be required for secretion of the dimeric form.     

Response to acute hCG stimulation and steroidogenic potential of Leydig cell fibroblastic precursors in humans

The process of early testosterone (T) secretion and Leydig cell differentiation in humans was studied to explore the steroidogenic capacity of Leydig cell fibroblastic precursors. Seven cryptorchid boys received hCG prior to orchidopexy. Patients CP, PB, and MR received one injection of 1000 IU; patients JR and GG, three daily injections of 1000 IU, and patients MP and MM, five daily injections of 1000 IU. A testicular biopsy was obtained at the time of operation, 24 hours after the last injection. Serum T (ng/dl) before and after hCG stimulation and testicular T (ng/g) were determined by RIA. A control prepubertal testis (tumoral orchidectomy) was incubated in vitro and showed a time-dependent accumulation of T both in the medium and the testicular tissue. Testosterone released into the medium at 1, 2, and 4 hours was 0.76, 1.43, and 4.03 ng/ml, respectively. Tissue T at 0, 1, 2, and 4 hours was 9, 11, 16, and 24 ng/g, respectively. This indicates synthesis and secretion of T into the medium. Control testes showed abundant fibroblastic precursors with scanty cytoplasm, few organelles, heterochromatic nuclei, and minute nucleoli. No Leydig cells were present. After 1 day of hCG stimulation, numerous fibroblasts were activated, displaying enlarged cytoplasms with increased numbers of organelles, nuclei rich in euchromatin, and bigger nucleoli. No Leydig cells were present. Basal serum testosterone was 58.2 +/- 45.3 ng/dl and 87.3 +/- 42.0 after hCG administration, while testicular T was 974.0 +/- 686.0 ng/g (control prepubertal testicular T is 10-50 ng/g). After 3 days of hCG, activated fibroblasts increased and immature Leydig cells appeared. Basal serum T was 35.5 +/- 7.8 ng/dl and 394.0 +/- 24.0 after hCG stimulation, while testicular T rose to 2797.5 +/- 1222.6 ng/g. After 5 days, mature Leydig cells appeared for the first time. Serum T was 58 +/- 59.3 ng/dl (basal) and 641.5 +/- 390 ng/dl (after hCG); testicular T was 789 ng/g (patient MM did not have a value for testicular T). HCG induced numerous coated pits and endocytic vesicles in activated fibroblasts and young Leydig cells, suggesting receptor aggregation and internalization of hormone-receptor complexes. Peroxidase-antiperoxidase (PAP) localization of T was positive in peritubular fibroblasts and Leydig cells.(ABSTRACT TRUNCATED AT 400 WORDS)     

Heterogeneity of adult mouse Leydig cells with different buoyant densities.

The authors investigated the morphologic characteristics and human chorionic gonadotrophin (hCG)-stimulated testosterone production of adult mouse Leydig cells in vitro, which have different buoyant densities. Leydig cells from five testes of Swiss outbred male mice (15 weeks old) were isolated and purified by mechanical dispersion followed by density gradient centrifugation using Percoll. Two groups of Leydig cells were obtained with different buoyant densities: group 1 had densities of 1.0667 to 1.0515 g/cm3 and group 2 had densities of 1.0514 to 1.0366 g/cm3. In vitro testosterone production of these Leydig cells, in response to different doses of hCG (0, 5, 25, 125, 625, and 3125 pg/mL), was determined by radioimmunoassay. Leydig cells were fixed and processed for electron microscopic stereology to quantify the organelles by volumes and surface area. In Leydig cells of Group 1, testosterone production per cell in vitro in response to 0 and 5 pg/mL hCG was not significantly different (P greater than 0.05). Increases in the dose up to 25 pg/mL produced a significant increase (P less than 0.05) in testosterone production, although hCG doses of 125 and 625 pg/mL did not produce further increases in testosterone levels. However, 3125 pg/mL hCG further elevated the testosterone production by those Leydig cells with high buoyant density. In Leydig cells in group 2, the patterns of testosterone production in response to hCG doses of 0, 5, and 25 pg/mL were similar to those of Leydig cells in group 1. Those Leydig cells with low buoyant density, however, were unable to stimulate further testosterone production by an hCG dose of 3125 pg/mL.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regulation of steroidogenesis by Cordyceps sinensis mycelium extracted fractions with (hCG) treatment in mouse Leydig cells

The in vitro effect of extracted fractions of Cordyceps sinensis (CS) mycelium on hCG-treated testosterone production from purified normal mouse Leydig cells was examined. Different fractions extracted from CS (F1-water soluble polysaccharide, F2- water soluble protein and F3- poorly water soluble polysaccharide, and protein) were added to Leydig cells with hCG, and the production of testosterone was determined by radioimmunoassay (RIA). Testosterone productions stimulated by hCG in mouse Leydig cells were suppressed by F2 at 10 mg/ml and F3 at doses from 3 to 10 mg/ml, respectively. F2 and F3 at 10 mg/ml did inhibit dbcAMP-stimulated testosterone productions which indicated that F2 and F3 might affect steroidogenesis at the site after the formation of cyclic AMP. Finally, cycloheximide inhibited F2- and F3-treated mouse Leydig cell testosterone production.     

Studies on LH modulated 8kDa peptide involved regulation of testosterone production in rat Leydig cells

Aim: To demonstrate the role of the 8 kDa peptide in regulation of testosterone production by mt Leydig cells. Meth-ods: A peptide similar to 8 kDa peptide purified from immature rat Leydig cells was isolated and purified from rat lungcytosol. Immunological and structural similarity between the peptides purified from lung and Leydig cells was estab-lished by Western blot and tryptic map comparison respectively. Results: Addition of the 8 kDa peptide 10, 50, 100;and 150 ug decreased the production of testosterone in Leydig cells dose-dependently. But the addition of the peptide150 ug along with hCG had no effect on hCG-stimulated increase in testosterone production. Conclusion: In vitro ad-dition of the peptide purified from lung cytosol to adult rat Leydig cells resulted in a concentration-dependent decrease inbasal testosterone production although it had no effect on hCG-stimulated testosterone production. (Asian J Androl1999 Dec; 1: 191-194)     

Developmental changes in in vitro testosterone production by dispersed Leydig cells during fetal life in rats

The age-related evolution during fetal days 18.5-21.5 of the capacity of collagenase-dispersed Leydig cells to produce testosterone and to respond to LH or dibutyryl cyclic AMP (dcAMP) was studied in vitro in the rat. When dispersed Leydig cells were incubated in control medium, testosterone secretion by cells from 18.5-day-old fetuses during the first 5 h was 100 and 50% higher than secretion by cells from 20.5- and 21.5-day-old fetuses, respectively. The secretion maximally stimulated by 100 ng/mL LH or stimulated by 1 mM dcAMP was also stronger on day 18.5 than on days 20.5 and 21.5 during the first 3 h of culture. The dose-response curves for LH showed that the ED50 was similar for day 18.5 and 20.5 cells (2 ng/mL LH). During the course of 24-h incubation, the secretion rates also changed with time and fetal age: Between 5 and 24 h of culture basal secretion decreased in day 18.5 cells, rose slightly in day 20.5 cells, and increased sharply in day 21.5 cells; in the same way, in the presence of LH or dcAMP, the secretion by day 18.5 cells decreased faster than that of day 20.5 or 21.5 cells. The basal testosterone secretion of the Leydig cells and its maximum steroidogenic capacity decrease during late fetal life in the rat, and there was no change in the sensitivity to LH during this period. The age-related differences in the variations of the secretion rates as a function of the duration of incubation suggest the existence of an evolution in extragonadotropic regulations during late fetal life.     

Prolonged histamine deficiency in histidine decarboxylase gene knockout mice affects Leydig cell function

The present study focuses on histaminergic regulation of Leydig cell physiology, since limited information is available so far. To evaluate the dependency of Leydig cells on histamine (HA), we performed experiments using highly purified Leydig cells in culture, isolated from wild type (WT) and histidine decarboxylase (Hdc) gene knockout (HDC KO)-so HA-deprived-mice. HDC KO Leydig cells showed lower basal and human choriogonadotropin (hCG)-induced testosterone production compared to WT Leydig cells, presumably due to altered P450scc gene (Cyp11a1) expression levels. Moreover, in HDC KO cells, hCG did not increase basal expression levels of HA H1 and H2 receptor genes, while the hormone showed a significant inducing effect in WT cells. Based on these findings, we propose that prolonged HA deficiency in HDC KO mice affects various aspects of Leydig cell physiology, most importantly the response to hCG, providing definite evidence that HA plays a role as direct modulator of Leydig cell function and steroid synthesis in the testis. Also, the results presented herein constitute the first molecular evidence for the expression of HA H1 and H2 receptor subtypes in isolated Leydig cells.     

老年大鼠睾丸间质细胞结构和功能变化的实验研究

目的:研究老年SD大鼠(PADAM动物模型)睾丸间质细胞形态、分泌功能变化,探讨老年大鼠睾丸间质细胞的功能状态。方法:分别取青年SD大鼠和老年各20只,静脉血测定血清总睾酮和游离睾酮的浓度,并通过组织切片和透射电镜观察两个年龄组大鼠睾丸间质细胞形态学变化;此外,分别用hCG、Forskolin刺激体外培养的两个年龄组大鼠的睾丸间质细胞,比较培养基中睾酮和孕酮的浓度。结果:老年大鼠的血清总睾酮[(3.07±0.75)nmol/L]和游离睾酮[(0.71±0.65)nmol/L]均比青年大鼠[(10.89±6.11)nmol/L和(2.42±1.02)nmol/L]显著降低(P<0.05);细胞形态有较显著差异;体外培养的大鼠睾丸间质细胞分泌能力显著降低(P<0.05)。结论:老年SD大鼠血清睾酮和游离睾酮浓度显著低于青年SD大鼠,原因在于睾酮合成酶系统整体功能衰退。     

Human testicular LH receptors: correlations with circulating gonadotrophins and testicular steroid secretion

Testicular androgen production is regulated by circulating LH, the effect of which is mediated by its testicular membrane receptors. In the present study, testicular [¹²⁵I]hCG binding in man was investigated and found to be characterized by saturability and high affinity (mean K_D in testes of 21 patients with prostatic carcinoma = 1.64 times 10^-10 M), and stimulated testosterone production in dispersed interstitial cells in vitro. The concentrations of the LH receptors correlated with serum FSH concentrations (r = 0.52, P < 0.05) but not with circulating LH levels. Neither had they any correlation with intratesticular testosterone, 5α-dihydrotestosterone, androstenedione, progesterone, 17-hydroxyprogesterone or pregnenolone concentrations, which may be due to the fact that LH receptors are confined to Leydig cells, whereas steroids may be unevenly distributed in the different cells of the testis. In contrast, the concentrations of the LH receptor displayed positive correlations with the concentrations of testosterone (r = 0.81, P < 0.001), androstenedione (r = 0.54, P <0.05), 17-hydroxyprogesterone (r = 0.76, P <0.001) and progesterone (r = 0.60, P < 0.05) in the spermatic vein serum of the patients. Our data suggest that the Leydig cells mainly responsible for steroid secretion into the blood are under gonadotrophic control exerted via their receptors, whereas Leydig cell function is not rapidly reflected in steroid concentrations within the testis itself.     

Serum testosterone response to desialylated human choriogonadotropin in man

To assess the in vivo steroidogenic activity of desialylated human choriogonadotropin (hCG) in man, highly purified desialylated hCG was administered as a constant intravenous infusion over 6 hours to four normal men at a rate sufficient to maintain substantial levels of desialylated hCG in the serum. The mean percent change of serum testosterone from baseline during the first 6 hours in men given an infusion of desialylated hCG was compared to that in saline-infused controls and that in men given highly purified intact hCG. The mean change of serum testosterone at 6 hours in the group infused with desialylated hCG (129% of baseline) was significantly greater than that of the controls (69% of baseline). Furthermore, the response to desialylated hCG could not be distinguished from that of hCG (125% of baseline). It was concluded that desialylated hCG, when given as a constant intravenous infusion, can elicit a substantial serum testosterone response comparable to that seen with purified hCG, and thus, that desialylated hCG behaves as an agonist of the LH/CG receptors on human Leydig cells.     

The influence of human chorionic gonadotrophin (hCG) on the morphology of the prepubertal human undescended testis

The effect of hCG-treatment on the morphology of the undescended testis was studied in testicular biopsies from 36 prepubertal boys operated on at intervals of 1 day to 2 years after discontinuation of hormonal treatment. Immediately after treatment, mature Leydig cells were observed, and the Sertoli cells were increased in size; serum testosterone had increased to adult levels. All these changes were reversible as judged from the material taken one month or more after the last hCG injection. Based on the observations and the results of a previous study it is suggested that hCG treatment does not induce any premature onset of Sertoli cell or germ cell maturation either in the undescended or in the contralateral testis.     

Effects of bromocriptine on pituitary-testicular function in the rat: possible inhibition of in vitro production of androgen by Leydig cells

The effect of bromocriptine (BR) on pituitary-testicular function has been investigated in vivo and in vitro in adult male rats. Testosterone production in vitro by collagenase- dispersed Leydig cells from 84-day-old rats was evaluated in the presence and absence of hCG and/or different doses of BR. In the presence of 1.5 X 10^-5 M BR, both basal and hCG-stimulated testosterone production were decreased whereas at lower doses BR was ineffective. In vivo 60-day-old rats were injected sc with BR (150 μg/rat or 750 μg/rat twice daily) or vehicle for 24 days. This treatment reduced the plasma level and pituitary content of prolactin, slightly increased the plasma levels of LH and FSH but did not affect pituitary gonadotrophin content. Irrespective of the dose of BR injected, plasma levels of androgen did not change, but with the large dose of BR a decrease in testicular content of testosterone (P = 0.05) was observed. In the same animals the number of LH/hCG receptors was significantly reduced, and the sensitivity of the isolated Leydig cells to hCG stimulation in vitro was reduced; however, both the basal secretion and the maximum testosterone response to hCG were unaffected. These results show impairment of pituitary-testicular function in BR-treated rats, either as a result of BR-induced hypoprolactinaemia or as a consequence of direct effects of BR on the Leydig cells.