In vitro effects of Celiptium and MR 14504 on mature rat Leydig cell testosterone production

Percoll-purified mature rat Leydig cells have been used to evaluate the testicular toxicity of two highly potent intercalating agents (Celiptium and MR 14505). Testosterone secretion in the absence and in the presence of human chorionic gonadotropin (hCG) was measured to assess Leydig cell function. Celiptium and MR 14504 induce time- and dose-related inhibitory effects on the production of testosterone by Leydig cells, both in the presence and in the absence of hCG, whatever the concentration of hCG used. We have observed that MR 14504 is about 5 times more potent as an inhibitor of rat Leydig cell steroidogenesis than Celiptium without inducing any cell toxicity. The present study indicates that the Leydig cell is an additional potential site for the primary toxic effects of these drugs in the adult rat testis.

Equine cytochrome P450 aromatase exhibits an estrogen 2-hydroxylase activity in vitro

Aromatase (estrogen synthetase) is a steroidogenic enzyme complex which catalyzes the conversion of androgens to estrogens (termed aromatization). This enzyme was purified from adult equine testis to homogeneity by five chromatographic steps. The ability of purified and reconstituted equine aromatase to exhibit an estrogen 2-hydroxylase activity was tested and compared to testosterone aromatization. Enzymatic activities were assessed by tritiated water release from labelled estradiol and testosterone. Kinetic analysis of estradiol 2-hydroxylation showed an apparent K(m) of 23 microM and a V(max) of 18 nmol/min/mg, whereas the values for testosterone aromatization were a K(m) of 15.7 nM and a V(max) of 34.6 pmol/min/mg. A specific antiserum raised against purified testicular equine P450arom and known to inhibit aromatase activity [1] was also found to inhibit the estrogen hydroxylase activity of equine placental microsomes in a dose-dependent manner with an IC50 value of 15 microl serum: 0.5 ml incubate. The estrogen hydroxylase activity was inhibited in a dose-dependent manner by two classes of aromatase inhibitors, i.e. steroidal-- (4-hydroxyandrostenedione and 7alpha-([4-aminophenyl]thio)-androst-4-ene-3, 17-dione)--and non-steroidal--(fadrozole and miconazole). The IC50 values were approximately 300 and 890 nM for 4-hydroxyandrostenedione and 7alpha-([4-aminophenyl]thio)-androst-4-ene-3, 17-dione, and 92 and 285 nM, for fadrozole and miconazole, respectively. Furthermore, 4-hydroxyandrostenedione caused a time-dependent inactivation of estrogen hydroxylase activity. We conclude that equine aromatase is able to use estradiol as a substrate, and converts it to catechol estradiol in vitro, possibly using the active site of aromatization. This is the first demonstration that equine aromatase functions as an estrogen 2-hydroxylase, in addition to transforming androgens into estrogen.

Enzymatic properties of adult human Sertoli cells in vitro

The adult human Sertoli cells produced lactate, estradiol-17beta, transferrin and inhibin; germ cells modulate synthesis of these compounds. In order to study the functional features of human Sertoli cells in vitro, the aim of this study was to measure the lactic dehydrogenase (LDH), gamma-glutamyl transpeptidase (GGT), alkaline phosphatase (ALP) and creatine kinase activities (CK) in primary cultures of Sertoli cells prepared from young men (mean age: 29 years, n = 11). Five LDH isozymes have been found in Sertoli cells, the main fractions being the LDH3 and LDH4; each of them represented 30% of the total LDH activity. Furthermore, CK and ALP activities were measured in Sertoli cells. It is of note that the Sertoli cell ALP activity was 50% lower than that of germ cells. Whatever the Sertoli cell parameter measured herein, there is a great variability between patients and FSH (dbc AMP, as well as retinol, insulin, testosterone) is poorly effective in improving these enzymatic activities in vitro. We have confirmed that GGT was exclusively present in Sertoli cells and thus may be considered as a specific marker. LDH is involved in Sertoli cell glucose transformation and thus provided energetic substrates for germ cells. In contrast, the roles of CK and ALP remains to be clarified. In conclusion, we have demonstrated the existence of several enzymes namely LDH, GGT, ALP and CK in Sertoli cells prepared from adult human testis.

Postprandial lipoprotein metabolism in normotriglyceridemic non-insulin-dependent diabetic patients: influence of apolipoprotein E polymorphism

Non-insulin-dependent diabetes mellitus (NIDDM) is associated with postprandial lipoprotein clearance defects that are correlated with the fasting hypertriglyceridemia widely observed in NIDDM patients. The aim of this study was to determine if such postprandial disturbances are found in NIDDM patients strictly normotriglyceridemic in the fasting state, and if the apolipoprotein E (apo E) polymorphism influences postprandial metabolism of intestinally derived lipoproteins. The vitamin A-fat loading test was used in 18 normotriglyceridemic NIDDM patients and seven normotriglyceridemic obese controls, and postprandial triglyceride (TG) and retinyl palmitate (RP) concentrations were evaluated in total plasma, and in the chylomicron (Sf > 1,000) and nonchylomicron (Sf < 1,000) fractions isolated by ultracentrifugation. NIDDM patients exhibited an amplified response of both TG and RP as compared with obese controls in the three fractions. Incremental TG response to the oral fat load was strongly correlated with fasting TG level (r = .80, P < .0001) in the whole study population. Postprandial lipoprotein profiles were distinguished in NIDDM patients according to apo E phenotype: despite normal fasting TG levels in E3/3 (n = 6), E2/3 (n = 6), and E3/4 (n = 6), postprandial RP response was twofold to threefold higher in E2/3 and E3/4 patients than in the common E3/3 phenotype. Contrasting lower postprandial TG increment and lower fasting and postprandial high-density lipoprotein (HDL) and HDL3 cholesterol levels were observed in E3/4 versus E3/3 patients, possibly reflecting modifications in lipid content of the postprandial lipoproteins driven by a differential lipid transfer activity depending on apo E isoform. These data indicate an enhanced postprandial lipemia in normotriglyceridemic NIDDM patients, and demonstrate the influence of apo E polymorphism on their lipoprotein clearance. Postprandial alterations of lipoprotein remnants may thus accelerate atherogenesis even in normotriglyceridemic NIDDM patients.

Germ cell and Sertoli cell interactions in human testis: evidence for stimulatory and inhibitory effects

In human Sertoli cell preparations obtained from healthy men (mean age 31.8 +/- 6.8 years; n = 6), we have measured the productions of lactate, 17 beta-oestradiol, transferrin and inhibin between day 4 and day 5 after plating, either in the presence or absence (hypotonic treatment of plated cells on day 2) of germ cells. The results, expressed per 10(6) of cells plated/24 h, showed that lactate production was unchanged, whether or not germ cells were present. However, if we calculated the lactate production per mg protein/24 h, the lactate output was decreased (30-60%) in the presence of germ cells. Whatever the mode of expression, Sertoli cell 17 beta-oestradiol synthesis was diminished 1.5-fold in the presence of germ cells. Conversely, the transferrin output was increased 3.2-fold in non-treated Sertoli cell preparations when compared to the hypotonic-treated plates. A similar observation was recorded for the in-vitro production of inhibin by Sertoli cells, which was enhanced 1.4-fold when germ cells were present. These results, together with a likely potentializing role of germ cells on follicle stimulating hormone control of Sertoli cell function, strongly suggest that germ cells exert both stimulatory and inhibitory effects in regulating human Sertoli cell function through either direct contact and/or via secreted factors.

Steroidogenesis in the two enriched-Leydig cell populations of human testis: evidence for a positive control by seminiferous tubules secreted factor(s)

In two different enriched populations of Leydig cells (called FI and FII) obtained from human testes (young patients: mean age 36 +/- 3 years, n = 6; aged men: mean age 73 +/- 2 years, n = 5), the dehydroepiandrosterone and testosterone in vitro outputs were increased in a dose- and time-related manners by hCG. Similar results were obtained when the Leydig cells were incubated in presence of either dbcAMP or 22R-hydroxycholesterol. In presence of either hCG or dbcAMP, the coefficient of stimulation (in terms of steroid outputs) was higher in FII when compared to FI. Conversely, the basal production of steroids was greater in FI than in FII, mainly for testosterone. The addition of increasing amounts of seminiferous tubule culture medium (STM) to the Leydig cell incubation medium led to a dose-related enhancement of the steroid production in both enriched-Leydig cell fractions under basal and hCG-stimulated conditions. Similar results were obtained in presence of increased seminiferous tubules length. Additional experiments realized with either concentrated STM or the coculture of seminiferous tubules with purified Leydig cells have confirmed the existence of a paracrine control of Leydig cell steroidogenesis by seminiferous secreted factor(s). A paracrine factor (or factors) from seminiferous tubular origin influences positively and with a high efficiency the Leydig cell function in humans, whatever the age.

Human Sertoli cells in vitro. Lactate, estradiol-17 beta and transferrin production

Human Sertoli cell parameters, namely lactate, estradiol-17 beta, and transferrin production, were determined after a 24-hour incubation with either human follicle stimulating hormone (FSH) or dbcAMP in the presence or absence of testosterone plus a phosphodiesterase inhibitor (1-methyl-3-isobutylxanthine; MIX). Testicular tissues were obtained from 10 young patients (mean age, 29 years); using a 3-step enzymatic treatment, Sertoli cell enriched preparations (> 92%) were studied after 4 days as primary cultures. No significant changes in lactate, estradiol-17 beta, and transferrin outputs have been observed according to age in patients ranging in age from 16 years to 47 years. Sertoli cell production of the compounds is controlled by testosterone plus MIX; FSH (or dbcAMP) treatment only slightly improves their synthesis. It is suggested that human Sertoli cell function, as far as the parameters measured in this study are concerned, is likely regulated by cAMP-dependent and independent pathways.

Germ cell-Sertoli cell interactions and production of testosterone by purified Leydig cells from mature rat

The addition of seminiferous tubule (ST) culture medium (STM) prepared from testes of either busulfan-treated (Bus) or cryptorchid (Cryp) or genetically sterile (hd) rats, to Percoll purified Leydig cells leads to a further increase of LH-stimulated testosterone (T) output (26, 43 and 14%, respectively). Taking into account that the Sertoli cell number per cm of ST is 2.6, 1.8 and 1.4-fold greater in Bus, Cryp and hd rats than in controls, the above STM effects on T output, expressed per 10(6) Sertoli cells are in fact lower (63, 44 and 43%, respectively) that those of control STM. Similar results have been obtained for the STM transferrin levels which are decreased, 74, 67 and 45%, respectively in Bus, Cryp and hd animals. So, it is likely that the Sertoli cell secretion of both the paracrine factor involved on Leydig cell T production and the transferrin is influenced mainly by spermatids and to a lesser extent by spermatocytes of mature rat testis.

Age-related changes in the function of the pituitary-gonadal axis in a sterile male rat mutant (hd/hd)

Testicular growth is depressed in the genetically sterile male rat (hd/hd) relative to its LE phenotype littermates (by 50% and 73% at 27 and 90 days of age, respectively). Within the hd/hd testis, both the tubular and seminiferous tubule tissues are affected by the mutation. In addition, there is significantly less germ cell production from the primary spermatocyte stage of spermatogenesis onwards and the total number of Sertoli cells observed is less. In the intertubular tissue, the total volume and the total number of Leydig cells per testis is significantly less, but the mean volume of an average Leydig cell is not modified. The serum gonadotropin levels are higher in the hd/hd rat, whereas from 40 days of age onwards the level of testosterone is lower. The FSH and LH binding affinity constants are unchanged by the mutation; however, the total number of FSH binding sites per 10(6) Sertoli cells is lower while that of LH per 10(6) Leydig cells is greater. Indeed, it is likely that the lesser concentration of serum testosterone in the hd/hd rat is a result of a smaller number of Leydig cells since their individual function is not modified. The testicular androgen binding protein (ABP) content and the ABP output towards the epididymis are lower as a consequence of both a lesser number and an altered function of the Sertoli cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for LH-inhibiting activity in ovine peripheral and testicular blood

Intracellular cyclic AMP and testosterone productions by purified mature rat Leydig cells were stimulated by oLH (25 micrograms/l) 18- and 12-fold, respectively, after a 5-h incubation period. The replacement of the incubation medium by charcoal-treated testicular venous plasma (40%, v/v) from adult rams in the breeding season induced an inhibition of cyclic AMP and testosterone productions (82 and 66%, respectively, of oLH-stimulated values). Testicular arterial plasma is less effective than testicular venous plasma, even when it originates from non-breeding season rams; in that case, testicular venous and arterial plasma strongly inhibit testosterone productions (84 and 67%, respectively of oLH-stimulated values), which probably indicates that the inhibitory activity is higher in the non-breeding season. The addition of peripheral plasma leads to a testosterone production equal to 35 and 65% of the oLH-stimulated values, respectively, for ram blood collected in non-breeding and breeding seasons. The same concentration of ovine testicular lymph or rete testis fluid is without significant effect on cyclic AMP production; however, testosterone is slightly decreased by lymph but enhanced by rete testis fluid. Increasing amounts of venous or arterial testicular blood induce a dose-related decrease of the specific binding of labelled hCG in both rat and ram testicular membranes. This inhibiting factor is present in peripheral and testicular blood of either control or hypophysectomized or castrated rams, is a protein in nature, heat-sensitive, and has an apparent molecular weight higher than 10,000 daltons.(ABSTRACT TRUNCATED AT 250 WORDS)

Combined diagnostic value of biochemical markers in acute pancreatitis

Eighty-three patients suffering from upper abdominal pain were studied to evaluate the contribution of commonly used biochemical markers in the diagnosis of acute pancreatitis. On admission to hospital, serum amylase, lipase, total bilirubin, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and gamma-glutamyl transferase activities were measured. By stepwise logistic discrimination, only two determinations appeared to be of clinical value: lipase and alkaline phosphatase activities. A classification rule was established including these two measurements and its diagnostic performance evaluated by a jackknifed method amounted .83%. ROC curves were used to assess sensitivity and specificity. Our study clearly shows that serum lipase measurements should be preferred to amylase measurements, and that our two-test classification rule provides an efficient aid in clinical decision-making.

Partial purification of androgen binding protein from bull epididymis

An androgen binding protein (ABP), with an equilibrium dissociation constant of 4.2 nM and a molecular weight of about 100 kDa, has been purified from bull epididymal extracts using a four-step procedure. These preliminary results underline the main difficulties encountered in the purification of this protein present at a very low concentration (i.e. 50-fold less than in rat or rabbit epididymides). Ammonium sulfate precipitation is not a suitable step due to the formation, in presence of salt, of insoluble material leading to a loss of ABP. Lipids, particularly phospholipids, might be implicated in this phenomenon. Several steps, including anion exchange in batch followed by concentration, affinity chromatography and HPLC gel filtration allowed us to obtain a 7667-fold purified protein with a 9% yield.

[Role of a purified Sertoli cell protein (CMB-21) in the biosynthesis of Leydig cell testosterone in the immature rat]

The existence of Sertoli cell factors which modulate the rat Leydig cell function prompted us to study the biological activity of selected proteins called CMB proteins and produced by immature rat Sertoli cells. Percoll purified Leydig cells (10(5)) from 20 days-old rats have been incubated 5 h at 32 degrees C in 1 ml Ham F12/DME medium with increasing concentrations of partially purified CMB proteins (0-1,000 ng/ml) either in presence or absence of oLH (25 ng/ml). Among the CMB proteins tested, only CMB-21 produces a dose related increase of testosterone production: from 2 to 500 pg/ml of CMB-21, testosterone output is unchanged (51 pg/10(5) cells) but 1 to 1,000 ng/ml of this protein produces a linear increase of testosterone productions (86 to 870 pg). In the presence of oLH which induces a 10-fold increase of testosterone production (499 pg), increasing doses of CMB-21 further stimulate testosterone output (775 to 2.272 pg/10(5) cells). Whatever the concentration of oLH used (0 to 50 ng/ml), CMB-21 (500 ng/ml) leads to a further 2 fold augmentation of testosterone synthesis; similarly, in the presence of dbcAMP (1 mM), CMB 21 increases the testosterone production but no effect is observed when Leydig cells are incubated in the presence of 22R-hydroxycholesterol (30 microM). The cAMP levels which are increased more than 4 fold by oLH, remain unchanged in the presence of CMB-21 either alone or with oLH, as observed when Sertoli cell culture medium is used.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro effects of growth factors on rat germ cell RNA synthesis and their modulation by Sertoli cell-secreted proteins

In vitro rat germ cell RNA synthesis is influenced by growth factors. Basic fibroblast growth factor (0.1 to 100 ng/ml) increases [3H]uridine incorporation in round spermatids (RS) but not in pachytene spermatocytes (PS); this effect is potentiated by insulin (10 micrograms/ml) and blocked in the presence of Sertoli cell-secreted proteins (SCSP). Somatomedin C (0.1 to 100 ng/ml) exhibits a similar effect when used alone without an influence by SCSP. Transforming growth factor beta (0.1 to 10 ng/ml) acts on both cell types, but SCSP amplify this effect only in PS. These data suggest that growth factors synthesized in situ may play a role in the germ cell development and that their effects are modulated by SCSP.

[Paracrine regulation of Leydig cell aromatase in the rat: development with age]

The paracrine regulation of rat testicular aromatase activity has been studied at various ages (20, 30, 45, 55, 70, 240 days); seminiferous tubule culture medium (STM) have been prepared at the above ages and added (40%, v/v) to the Percoll purified Leydig cells (150,000) for 5 h at 32 degrees C in presence or absence of oLH (25 ng/ml). In 20 day-old rat, the basal oestradiol-17 beta (E2) output is low (20 pg/10(6) Leydig cells), then gradually increases until day 70 (280 pg) without any change at 240 days (260 pg). In presence of oLH, a 2 fold increase of E2 output is observed whatever the age and the addition of STM further enhances both the basal (21-41%) and the LH-stimulated (14-65%) E2 syntheses. In conclusion, the Leydig cell aromatase activity, is in part regulated by STM factors, mainly after puberty. From 20 days onwards, it is noteworthy, that the Leydig cell testosterone (T) synthesis is highly stimulated by oLH (10 fold) and the addition of STM further increases T outputs (2 fold) which brings about a high intratesticular T level necessary for development of spermatogenesis.

Validation of a new system for androgen binding protein measurement

A new technique that permits measurement of Androgen-Binding Protein (ABP) is validated by reproducibility, linearity and correlation studies. Using this apparatus allowing Scatchard plot analysis, it is also possible to measure association and dissociation rate constants. In addition, it is a very useful tool for a rapid screening of ABP binding capacity during a chromatographic stepwise purification.

Changes in androgen binding protein (ABP) production following continuous low dose gamma irradiation (IR) of adult rat

Continuous low dose gamma irradiation induces a progressive degeneration of germ cells with a concomittant increase in blood FSH; however, the Sertoli cell function is not too much altered since serum ABP level is normal and it is likely that the decrease of epididymal ABP content is the consequence of a reduction in seminiferous tubule fluid excretion. Obviously, spermatids seems to be involved in the regulation of Sertoli cell ABP synthesis.

Stimulation of adult rat Leydig cell aromatase activity by a Sertoli cell factor

The paracrine control of adult rat Leydig cell aromatase activity was investigated in vitro. After a 24-h preculture period of Percoll-purified Leydig cells (2.5-5 X 10(5) cells), 17 beta-estradiol synthesis reached a maximum at 5 h in the presence of exogenous testosterone (200 ng/ml) as substrate, with or without LH (100 ng/ml), and remained stable for a further 24 h. Aromatase activity was stimulated 2.5-fold by LH. The addition of seminiferous tubule culture medium (STM) from normal, neonatally hemicastrated, or prepubertally irradiated rats as well as Sertoli cell culture medium prepared from these animals enhanced both basal and LH-dependent aromatase activities during 5 h; this effect was diminished after 24 h of culture. When seminiferous tubules (200 mm) were cocultured with Leydig cells, a greater stimulation of 17 beta-estradiol production was observed compared to culture with STM. The association of Sertoli and germ cells with purified Leydig cells further enhanced aromatase activity. These results demonstrate that a Sertoli cell factor regulates Leydig cell aromatase activity. This factor is of proteic nature, thermolabile, has a mol wt ranging between 10,000-50,000, and is different from the LHRH-like substance. This compound is tissue and species specific, since it is not present in rat serum, other cell line media, or guinea pig and mouse STM. Its secretion is independent from FSH and testosterone controls. The stimulation of aromatase activity by this factor requires protein synthesis.

Effects of cisplatin and bleomycin on mature rat Leydig cell testosterone production

A single i.p. injection of either cisplatin or bleomycin affects the testosterone production by the Leydig cells in mature rats. It is noteworthy that on day 30 after treatment, a complete recovery of Leydig cell function is found in bleomycin-treated rats whereas in cisplatin-injected animals, 25-48% decreases of testosterone synthesis are still observed, respectively, under basal and LH-stimulated conditions. Together with the germ cell destruction, the low testosterone levels probably contribute to the sterility in cisplatin-treated rats.

Effect of continuous low-dose gamma-irradiation on rat Sertoli cell function

Continuous low-dose gamma-irradiation of mature rats induced a progressive degeneration of the germ cells. Blood FSH increased by 127, 176 and 214%, respectively, after 55, 70 and 85 days of treatment when compared to FSH levels in control rats (8.50 +/- 0.60 ng/ml); conversely, serum LH and testosterone levels were unchanged. The Sertoli cell function was affected by the treatment from 70 days on, as attested by androgen binding protein (ABP) and transferrin secretions which diminished 35-40%. Serum ABP levels were not altered, whatever the duration of irradiation, even though epididymal ABP contents (as well as concentrations) diminished 34-60% when compared to those of the controls. Moreover, in purified Leydig cells, LH-stimulated intracellular cAMP levels, which were decreased by seminiferous tubule medium (STM) from control rats, were enhanced in presence of STM from treated animals. Testosterone output was stimulated 9-fold in presence of oLH and further increased (46-76%) from stages XIV-V by STM prepared from control and irradiated rats, respectively. After 85 days the STM effects on both cAMP and testosterone syntheses were zero. These results demonstrate a probable alteration of Sertoli cell function after irradiation, but also a role of the germ cells in the regulation of the synthesis of ABP, transferrin and Sertoli cell paracrine factors.

A minicolumn apparatus for androgen-binding protein measurement

An easy, rapid, and sensitive assay that permits measurements of androgen-binding protein (ABP) in tissue as well as in spent media from Sertoli cells is described; this method involves the specific binding of labeled dihydrotestosterone (DHT) to ABP. The apparatus holds 36 minicolumns loaded with a DEAE Bio-Gel matrix. A peristaltic pump is used for the free fraction elution, taking into account the extremely rapid rate of dissociation of the ABP-DHT complexes. This technique, which allows Scatchard plot analysis, has been used to measure the rates of association (5.15 X 10(5)M-1 S-1 and dissociation (21.32 X 10(-4) S-1; t 1/2 = 5.5 min): the ratio of these rate constants is in perfect agreement with equilibrium dissociation constants determined by Scatchard plot analysis (KD = 4-4.5 nM). The intraassay and interassay coefficients of variation are 5 and 8%, respectively. A good correlation (r = 0.98) is obtained with the standard method of steady-state polyacrylamide gel electrophoresis below a value of 250 micrograms cytosolic proteins/gel. This apparatus, which allows either the measurement of ABP in 12 samples (in triplicates) at a saturating concentration or the analysis of two Scatchard plots (each of 6 points), is also very useful for a rapid localization of ABP during chromatographic purification.

Adult rat Sertoli cells secrete a factor or factors which modulate Leydig cell function

Production of testosterone and oestradiol-17 beta by Leydig cells from adult rats was stimulated by LH or dibutyryl cyclic AMP (10 and 2.5-fold respectively). The addition of spent medium from normal, hemicastrated or gamma-irradiated rat seminiferous tubule cultures, as well as from Sertoli cell cultures, to purified Leydig cells further enhanced both basal (44 and 53% for testosterone and oestradiol-17 beta respectively) and LH-stimulated (56 and 18%) steroid output. Simultaneously, a decrease (20-30%) in intracellular cyclic AMP levels was observed. This stimulating factor (or factors) secreted by the Sertoli cells is different from LHRH, is of proteinic nature and has a molecular weight ranging between 10,000 and 50,000; its synthesis is not controlled by FSH nor by testosterone. This factor(s) involved in rat Leydig cell steroidogenesis, at a step beyond the adenylate cyclase, does not require protein synthesis for testosterone formation whereas it does for oestradiol-17 beta production. It should be noted that a germ cell-Sertoli cell interaction modulates the synthesis of this factor(s).

Spent media from immature seminiferous tubules and Sertoli cells inhibit adult rat Leydig cell aromatase activity

Adult rat Leydig cell aromatase activity is stimulated 2.5 fold by LH or dbcAMP. Spent media prepared from seminiferous tubules or Sertoli cells of immature rats depress both the basal and the LH stimulated estradiol syntheses (25 and 20% decreases, respectively). These inhibitory effects are further enhanced when FSH is added to the culture medium of seminiferous tubules or Sertoli cells. Rat serum as well as culture media from other cell lines are ineffective while seminiferous tubule media from other immature animals (mouse, guinea-pig, calf) inhibit the aromatase activity. This Sertoli cell factor is a heat stable protein (molecular weight greater than 10 kDa), different from the LHRH-like Sertoli cell compound, which acts on the aromatase activity at a step beyond the adenylate cyclase.

Effects of the transmethylation inhibitor S-adenosyl-homocysteine and of the methyl donor S-adenosyl-methionine on rat Leydig cell function in vitro

In purified rat Leydig cells, the methyl donor S-adenosyl-methionine (SAM), increases significantly in a dose dependent manner the [125I]hCG binding as well as the productions of cAMP and of testosterone; the competitive inhibitor of methylations S-adenosyl-homocysteine (SAH), has an opposite effect. Associated to oLH, SAM further enhances the cAMP synthesis while SAH inhibits significantly the adenylate cyclase activity. With regard to testosterone synthesis, SAM potentiates the stimulating roles of oLH and dbcAMP (27 and 38% increases, respectively) although SAH diminishes testosterone productions (48 and 35%, respectively under oLH and dbcAMP stimulations). Scatchard analysis has shown that SAM (1.4 mM) increases the number of LH/hCG binding sites on Leydig cells while SAH (1.4 mM) decreases it; LH/hCG Ka values are not modified neither by SAM nor by SAH. These data suggest that the in vitro regulation of steroidogenesis in purified rat Leydig cells may involve methylation processes (presumably phospholipids are the potential substrates of these reactions) which modulates the transmission of the hormonal signal through the membrane and affects the testosterone synthesis at a step beyond the adenylate cyclase.

Effects of seminiferous tubule secreted factor(s) on Leydig cell cyclic AMP production in mature rat

The effects of spent media from seminiferous tubules (STM) on Percoll-purified rat Leydig cells were investigated. Intracellular and extracellular cyclic AMP (cAMP) accumulation and testosterone production were measured. After a 5 h incubation period, STM reduces both the basal and LH-dependent cAMP levels (38 and 20%, respectively for intra- and extracellular cAMP) while, simultaneously, a stimulation of testosterone production is observed (47 to 50%, respectively in the absence or presence of LH). The reduction of cAMP levels observed after 5 h is likely to be due to the potentiating effect of the STM factor on the LH-dependent initial rise of the cAMP level which, in turn, induces a desensitization of the Leydig cell adenylate cyclase. This substance is a thermolabile protein (Mr greater than 50 000) produced by the Sertoli cell, independent of FSH and testosterone controls, and different from the LHRH-like substance.

Rat testis 17 beta-estradiol: identification by gas chromatography-mass spectrometry and age related cellular distribution

The aromatization of testosterone into 17 beta-estradiol (E2) was assessed in purified Leydig and Sertoli cells from rats aged 10-80 days. E2 was identified by gas chromatography-mass spectrometry (GC-MS) and measured both by radioimmunoassay (RIA) and GC-MS associated with stable isotope dilution. A potent competitive inhibitor of the aromatase activity, 4-hydroxyandrostenedione (4-OH-A) was used to test the enzymatic specificity. The basal aromatase activity was present in both cell types whatever the age of the animals. The basal E2 levels did not vary in Sertoli cells while a gradual increase was noted in Leydig cells until day 40, followed by a slight decrease in mature rats. In 10-day old animals, the aromatase activity was localized in Sertoli cells and highly stimulated by FSH; on day 20, both Sertoli and Leydig cells synthesized E2 although E2 from Sertoli cell origin was still predominant. Starting on day 20 until adulthood, the aromatase activity was under LH control in Leydig cells with a maximum around 40 days. The FSH and LH effects were mediated by cyclic AMP.

In vitro effects of prolactin and dexamethasone on rat Leydig cell aromatase activity

In Percoll purified adult rat Leydig cells, the estradiol secretion, in presence of exogenous testosterone (200 ng/ml) is stimulated 2-fold by either LH (100 ng/ml) or dbcAMP (1 mM). The addition of prolactin (1 microgram/ml) or dexamethasone (10(-7) M) to the Leydig cell incubation medium induces a 20% increase of the basal estradiol production, whereas, under LH or dbcAMP stimulations, 46 and 41% decreases are noted; moreover, a synergistic effect between prolactin and dexamethasone was observed in presence of dbcAMP leading to a 53% diminution of the estradiol synthesis. There results suggest that either hyperprolactinemia or high doses of glucocorticoids might inhibit the Leydig cell aromatase activity in presence of LH.

Effect of phorbol ester and phospholipase C on LH-stimulated steroidogenesis in purified rat Leydig cells

When the phorbol ester, 4 beta-phorbol-12-myristate-13-acetate (PMA) or bacterial phospholipase C (PL-C) is added to a preparation of purified adult rat Leydig cells, containing 2 mM CaCl2, a time- and dose-dependent decreases of LH-stimulated testosterone production is observed. After a 3 h stimulation with oLH (100 ng/ml), PMA (100 ng/ml) and PL-C (1.6 U/ml) do not affect the cell viability or the hCG specific binding, while cAMP accumulation is significantly reduced; cAMP-stimulated steroidogenesis is diminished only in the presence of PL-C. These observations suggest that in vitro: (i) activated Ca2+- and phospholipid-dependent protein kinase is implicated in the regulation of rat Leydig cell steroidogenesis by LH at a step before the adenylate cyclase; (ii) phospholipids play an important role in cAMP-stimulated testosterone synthesis.

Androgen-binding proteins in sheep epididymis: age-related effects on androgen-binding protein, cytosolic androgen receptor and testosterone concentrations. Correlations with histological studies

The androgen-binding protein (ABP) and the cytosol androgen receptor (Rc) were measured in the epididymis of sheep aged 50, 120 and 200 days. Specific binding protein was not detected at 50 days (infantile); near puberty (120 days), ABP was more concentrated in caput and cauda epididymal cytosols (117 and 183 fmol/mg protein respectively) than in corpus (53 fmol/mg) although Rc levels were low (3-5 fmol/mg). In postpubertal rams (200 days), ABP and Rc concentrations were higher in caput and cauda than in corpus epididymis. Testosterone concentrations at 50 days were not statistically different along the epididymis and varied from 0.3 to 0.8 pmol/mg protein. In 120-day-old animals, testosterone was more concentrated in caput and corpus (0.45 and 0.41 pmol/mg) than in cauda (0.17 pmol/mg); at 200 days, the testosterone contents were low (0.10-0.17 pmol/mg) in all parts of the epididymis. A ten-fold increase in plasma testosterone concentrations was observed between 50 and 200 days (1.31 to 11.71 nmol/l). Histological studies of the epididymis in the three groups of animals showed that the cell differentiation started in the cauda where the principal epithelial cells were higher (47-56 micron) than in the caput (31-38 micron) at 50 days. The principal cells of the caput were two- to threefold higher in postpubertal rams than in infantile lambs, a finding which is correlated with the levels of ABP and Rc. This may suggest an important physiological role of this region in the induction of sperm maturation.

Androgen-binding proteins in sheep epididymis: characterization of a cytoplasmic androgen receptor in the ram epididymis

An androgen receptor (Rc) was demonstrated in caput, corpus and cauda epididymal cytosols of the ram. This receptor had a high affinity for 5 alpha-dihydrotestosterone (Kd = 5.2 X 10(-9) mol/l) and could be distinguished from the androgen-binding protein (ABP) by several characteristics. On polyacrylamide-gel electrophoresis, Rc had a mobility of 0.37 and ABP 0.61; Rc sedimented in the 9S region of a linear sucrose gradient whereas ABP migrated in the 4.3S region; the molecular weights were 192 000 and 90 000 for Rc and ABP; their isoelectric points were 5.7 and 4.8-5.0; they were proteinaceous components since they were destroyed by proteolytic enzymes and heating (50 degrees C for Rc and 60 degrees C for ABP); they exhibited different half-times of dissociation:20 h at 0 degree C for Rc and 6 min for ABP, which is in agreement with their respective physiological roles, intra- and extracellular transport of androgens. The content of Rc-binding sites in caput epididymis was 18, in corpus 4 and in cauda 22 fmol/mg protein.

In vitro pregnenolone metabolism by mouse adrenal gland: II-Biosynthesis of androgens

Adrenal gland homogenates from four different strains of mice were incubated with (4-14 C)-pregnenolone and a NADPH generating system. The most important androgen synthesized was dehydroepiandrosterone; testosterone and progesterone were synthesized to a lesser extent and the production of androstenedione was very low. The highest synthetic activities were found in the high mammary tumor strain of mice (C3H x RIII) Fl; they were increased by ovariectomy, particularly when performed at two months of age. In the other strains, they were lower, specially in the low mammary tumor strain C 57 BL. However, the 3 beta-hydroxysteroid dehydrogenase / delta 5, 4 isomerase activity was not modified by ovariectomy in the high mammary tumor strain whereas it was increased in the low mammary tumor strains. These results indicate that the androgen synthesis in mouse adrenal depends on factors such as age, sex, endocrine status (ovariectomy) but also on susceptibility to mammary tumor development.

Interactions between prolactin and ovarian secretions during mammary tumorigenesis in the mouse

The plasma levels of ovarian steroids and the steroid binding capacity in the cytosol of mammary glands have been determined in the low-mammary-tumor C3H/f (XVII) mice. Implantation of a pituitary under the kidney leads to an increase of all these parameters as well as a high mammary tumor incidence. Simultaneous administration of the trans isomer of broparestrol (TBP) leads to a decrease of all the parameters.

Hormonal regulation of androgen-binding protein in lamb testes

Androgen-binding protein (ABP) was measured in the testes of 50-day-old lambs. The animals were hypophysectomized and treatment lasting for 5 days was begun 15 days after surgery. In hypophysectomized but otherwise untreated lambs (control group), no 5 alpha-dihydrotestosterone binding was detectable in testicular cytosol. One out of four lambs gave a positive response with FSH treatment (25 fmol ABP/mg protein), whereas a restoration of the synthesis of ABP was noted in all LH-treated animals (19 +/- 9 (S.E.M.) fmol ABP/mg, n = 4). No synergism between the two gonadotrophins was observed in lambs treated simultaneously with FSH and LH (19 +/- 4 fmol ABP/mg, n = 5). Testosterone treatment elicited a greater response (37 +/- 9 fmol ABP/mg, n = 5) than FSH or LH alone and the response was not increased by the simultaneous addition of FSH (38 +/- 10 fmol ABP/mg, n = 5). Whatever the treatment, no influence was observed either on the number of supporting cells (undifferentiated Sertoli cells) or the length of the seminiferous tubules (P>0.05); the diameter of tubules was significantly increased in the group treated with FSH and LH. It is postulated that testosterone may have a direct effect on the production of ABP by the supporting cells of the impuberal lamb.

Estradiol and progersterone receptors in F1 (C3H X RIII) mice mammary tumors: effect of castration

The estradiol binding capacity has been determined in the cytosol of spontaneous mammary cancer in the high-mammary-tumor F1 (C3H X RIII) hybrid mice. This binding is modified neither during tumor growth nor after ovariectomy. Since these tumors do not regress after ovariectomy, they are classified as ovarian-independent for their growth, although their estradiol binding capacity is maintained, at its low initial level.

[Testosterone metabolism in isolated cells of rat and ram seminiferous tubules]

Aspermatogenic seminiferous tubules were obtained from adult Wistar rats treated with Busulfan at the 20th day of foetel life. The isolated tubules converted 14C testosterone (T) into androstenedione (delta4), 3,5%) 5 alpha-dihydrotestosterone (DHT), (1%) ANd 5 alpha-androstane-3 beta, 17 beta-diol at unit gravity and incubated with 14C-T. Only delta was produced (2%). Using a similar technique the same result was obtained when pure preparation of round spermatids and primary spermatocytes from ram testis were incubated with 14C-T. From these experiments, we conclude that 5 alpha-reductase activity is present only in Sertoli cells.