Expression and immunolocalization of functional cytochrome P450 aromatase in mature rat testicular cells

Aromatase activity has been measured in Leydig cells and Sertoli cells from both immature and mature rats. Cytochrome P450 aromatase (P450arom) has been immunolocalized in germ cells of the rodent, bear, and rooster. Our purpose was to investigate expression of and to immunolocalize P450arom in adult rat testicular cells. After Western blotting with a specific anti-cytochrome P450arom antibody, we demonstrated the presence of a 55-kDa protein in mature rat seminiferous tubules and crude germ cell preparations. Immunoreactive aromatase was detected both in cultured rat Leydig cells and in testis sections (interstitial tissue and elongated spermatids showed positive immunoreactivity for P450arom). We next used reverse transcription-polymerase chain reaction to localize and quantify the P450arom mRNA in the various testicular cells. In rat Leydig cells, the amount of P450arom mRNA was 15 times higher than in Sertoli cells (34.1+/-3.2 to 2.3 +/-0.2 x 10(-3) amol/10(6) cells, respectively). In pachytene spermatocytes, round spermatids, and testicular spermatozoa the P450arom mRNA levels were 38.7+/-8.1, 20.4+/-3.8, and < 1.3 x 10(-3) amol/10(6) cells, respectively. The aromatase activity was 2.5-4 times higher in testicular spermatozoa (8.48+/-1.98 fmol/10(6) cells per hour) than in other germ cells. These results indicate that in mature rats, not only Leydig cells and Sertoli cells but also germ cells have the capacity to express functional P450arom. According to the germ cell maturation state, there was an inverse relationship between P450arom mRNA content and the biological activity of the protein. The expression of the functional P450arom in mature rat germ cells confirms the existence of an additional source of estrogens within the genital tract of the male.

Paracrine effect of seminiferous tubule factors on rat Leydig cell testosterone production: role of cytoskeleton

In Percoll purified Leydig cells from mature rat we have demonstrated that the basal testosterone production (9.5 ng/10(6) Leydig cells/24 h) is increased 10-fold in presence of a saturating amount of hCG (1 IU/mL) and diminished in a dose-related manner when larger concentrations of gonadotropin are used to reach 14 ng/10(6) Leydig cells for 50 IU of hCG. If 40% (v/v) seminiferous tubule medium (STM) is added together with hCG (1 IU/mL) to the incubation medium, a further increase (62%) of testosterone output is noticed. Obviously, when the testosterone production is low as a consequence of a higher dose of hCG (50 IU/mL), the STM (80%) improves the steroid synthesis five-fold (67.4 ng). Concerning the cytoskeletal components (microtubules, intermediate filaments and microfilaments) which have been examined in presence or absence of hCG and STM, we have found a rearrangement of cytoskeletal elements as well as cell-shape changes in relation with hormonal activity of the cells. The most prominent alterations of cytoskeletal elements have been observed after 24 h of incubation with 1 IU/mL of hCG added together with 80% of STM. The obtained results suggest that paracrine factor(s) presents in STM and acting in synergy with LH/hCG generate(s) the rearrangement of cytoskeletal structures which, in turn, facilitates the availability of cholesterol for the mitochondria and finally enhances the testosterone production in the rat Leydig cells.

IGF-1 stimulates synthesis of undersulfated proteoglycans and of hyaluronic acid by peritubular cells from immature rat testis

The exposure of confluent peritubular (PT) cells from immature rat testis to insulin-like growth factor-1 (IGF-1) induced a time and dose-dependent increase of [35S]-sulfate and [3H]-D-glucosamine incorporations in newly synthesized proteoglycans (PG). This increased content of PG was the result of an enhancement of PG synthesis rather than a decreased rate of degradation. IGF-1 had no effect on the molecular weight of synthesized PG nor on the nature and distribution of the constitutive glycosaminoglycan chains, both in medium and in cell layer. The stimulation of PG synthesis by IGF-1 appeared to be due, at least partially, to an increase of glycosylation processes. IGF-1 effect was mediated by the classical tyrosine kinase signalling process, since IGF-1 action on PG synthesis was abolished by genistein and tyrphostin A9, two well known tyrosine kinase inhibitors. The increase of PG synthesis was accompanied with an undersulfation of constitutive glycosaminoglycan (GAG) chains (chondroitin sulfate and heparan sulfate chains) since the [35S]/[3H] ratio was reduced by about 20-25% in presence of IGF-1. Although the mechanism of hyaluronic acid synthesis was completely different from those of other GAG, IGF-1 also dramatically enhanced its production by PT cells.

[Measurement of biological activity of hLH. Multicenter study]

This report describes the results of a multicentric study of biological methods for luteinizing hormone (hLH). The production of testosterone by animal Leydig cells is used by five laboratories with different methodologies including rat, mouse and pig cells. Dose-response curves of testosterone production, quality criteria and results on a physiological population of men and women, are reported and discussed. It is concluded that the bioactive determination of hLH must be considered as a reference method used in discordances between clinic and immunological methods.

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.

[In vitro gene expression of aromatase in rat testicular cells]

The ability of the male gonad to convert androgens into estrogens is well known; the microsomal enzymatic complex involved in this transformation is named aromatase and is composed of a specific cytochrome P450 aromatase (P450arom) and a ubiquitous reductase. Using a highly specific RT-PCR method we have measured the amount of P450arom mRNA in purified Leydig and Sertoli cells prepared from 20, 40 and 70-80 day-old rats. The amount of P450arom mRNA in the Leydig cells is independent of age (40 x 10(-3) attomoles/micrograms of total RNA); in contrast, in the immature rat Sertoli cells, after 5 days of culture the amount of P450arom mRNA is 20-fold lower when compared to that of 20-day-old rat Sertoli cells (71 x 10(-3) attomoles/micrograms of total RNA). Nevertheless, irrespective of the age, the addition of either FSH or dbcAMP for 6 h increases the level of P450arom mRNA in the rat Sertoli cell preparations. Therefore, we evidenced that during testicular maturation not only the Leydig cells but also the Sertoli cells of the rat have the capacity to express the gene for cytochrome P450 aromatase.

[Synthesis of proteoglycans by purified Leydig cells in immature rats and mature rats]

In Percoll purified Leydig cells from mature rat incubated for 24 h in Ham F12/DME medium, we demonstrated that the testosterone production (6 ng/10(6) Leydig cells/24 h) is increased 11 fold by a saturating amount of hCG whereas rat Leydig cells the basal output of testosterone is 4.5 ng and increased 2.5 fold by hCG. In the sulfate-free Ham F12/DME medium used for the proteoglycan (PG) studies, the productions of testosterone are lower but the cells remain sensitive to hCG. Whatever the age, the Leydig cells synthesize labeled PG after 24 h of incubation in the presence of [3H] glucosamine and [35S] sulfate. In immature rat, the quantity of synthesized PG is 20% higher than in mature animal; the secreted PG represented respectively 70 and 85% of the immature and mature Leydig cells PG outputs. In addition, the immature Leydig cell HSPG represents 15% of the secreted PG whereas it is 5% in mature rat; irrespective of the age the associated-HSPG account for 10% of the PG. The addition of hCG improves the production of HSPG especially in the immature Leydig cells. Therefore we evidenced a rat Leydig cell synthesis of PG, especially HSPG which are likely involved in the regulation of the Leydig cell function.

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.

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.

Evolution of somatic and germ cell populations after busulfan treatment in utero or neonatal cryptorchidism in the rat

In order to elucidate the respective effects of depletion of germ cells and of increase in testicular temperature, rats of the same Wistar strain were rendered experimentally bicryptorchid or sterilized by a busulfan injection in utero and compared to control animals. In both models, germ cells were depleted but numeric evolution and functions of somatic cells differed. The aim of that work was to compare the numeric evolutions of testicular somatic and germ cells to their respective functions in each model before puberty and in adult rats of the same strain. Serum concentrations of FSH, LH and testosterone were compared at 20, 40 and 110 days of age. Histological analyses of Sertoli and germ cells in the seminiferous tubules and of Leydig cells in the intertubular tissue were performed before puberty and at adulthood. Testosterone serum concentrations were depleted in both models starting at 40 days of age and more in busulfan-treated rats. Both FSH and LH levels were increased from 20 days onwards in experimental rats. Additional cryptorchidism in busulfan-treated rats depressed the serum testosterone concentration. At 17 days of age, the cryptorchidism do not modify somatic or germ cell populations while busulfan treatment has induced a decrease of both these populations. Conversely, the cross sectional area of the somatic testicular cells was not affected whatever the treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Effect of administration of a gonadotropin-releasing hormone (GnRH) antagonist (Nal-Glu) during the periovulatory period: the luteinizing hormone surge requires secretion of GnRH

In primates, the LH surge that triggers ovulation is induced by an increase in circulating estradiol (E2) levels. Although several studies suggest that E2 acts on the pituitary, it is still not clear whether GnRH is involved. We investigated the role of GnRH during the periovulatory period in normal women by treating them with the GnRH antagonist Nal-Glu ([Ac-D2Nal1,D4-ClPhe2,D3Pal3,Arg5,DGlu6 (AA),DAla10] when E2 levels exceeded 550 pmol/L. In the first study (A), Nal-Glu was administered in five regimens (n = 4 in each group): a single sc injection of 10 mg (group 1), a single injection of 20 mg (group 2), and an injection of 10 mg, sc, on 2 (group 3), 3 (group 4), and 5 consecutive days (group 5). In the second study (B; n = 4), Nal-Glu (10 mg, sc, on 3 consecutive days) was coadministered with E2 benzoate (EB; 0.5 mg, im, every 12 h on 3 consecutive days). Controls (n = 4) were treated with EB alone at the same stage of the cycle. In the third study (C), three women received 10 mg/day Nal-Glu, sc, on 3 consecutive days together with pulsatile GnRH therapy (25 micrograms/pulse, one pulse every 90 min, sc, for 3 days); the first pulse was given 12 h after the first Nal-Glu injection. In study A, gonadotropin suppression resulted in a transient decline in E2 in groups 1 and 2. Relative to control cycles, the LH surge occurred with a delay of 24-48 h in group 1 and 24-120 h in group 2. In groups 3, 4, and 5, Nal-Glu administration resulted in the demise of the dominant follicle in half of the women in each group. The remaining women showed a profile similar to that of groups 1 and 2, i.e. a transient decline in E2 levels followed by a recovery, and a LH surge occurring 4 +/- 0.3 days after the last Nal-Glu injection. In study B, simultaneous administration of Nal-Glu and EB induced a rise in E2 levels from 951.3 +/- 79.6 to 4000.1 +/- 772.5 pmol/L 24 h after the beginning of treatment. Serum LH and FSH levels both decreased and remained low throughout Nal-Glu treatment. None of the women showed a LH rise in response to the EB injection. In controls, however, EB administration was followed by a significant gonadotropin discharge 48 h after the first EB injection.(ABSTRACT TRUNCATED AT 400 WORDS)

[Production of Leydig cell testosterone in mature rats: mechanism of action of the Sertoli paracrine factor]

In Percoll purified Leydig cells from mature rat incubated in Ham F12/DME medium, we have demonstrated that the testosterone production (1 ng/10(6) Leydig cells/3 h) is increased 9 fold in presence of a saturating amount of oLH but diminished when larger doses of gonadotropin are used. However, if SCM or STM is added together with oLH to the Leydig cell incubation medium, a further increase (69%) of testosterone output is noticed. Obviously, when the testosterone production is low consecutive to a desensitizing dose of oLH, the STM or SCM improves at least 2 fold the steroid synthesis. Therefore, the paracrine factor (or factors) presents in SCM (or STM) which is testis specific and acts in synergy with dbcAMP and 22R-hydroxycholesterol, uses an alternative pathway to improve rat Leydig cell testosterone production since its biological effect is highly potent in absence and in presence of oLH. Therefore, these data bring new insights in the regulation of rat Leydig cell steroidogenesis through cAMP-independent channel suggesting either an increase of the cholesterol side chain cleavage activity and/or availability of the cholesterol to mitochondria.

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)

[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)

[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.

Age-related morphological and functional changes in the Leydig cells of the horse

Two ultrastructurally distinct types of Leydig cells were observed in the equine testis. Whereas the adult testis exhibited both postpubertal and adult Leydig cells, the testis of the pubertal horse contained only the postpubertal type, and that of the aged horse contained only the adult type. However, Percoll-purified testicular preparations from pubertal, adult, and aged horses all exhibited two distinct Leydig cell populations. The quantitative distribution and the functional characteristics of these Leydig cell populations (ability to bind human chorionic gonadotropin [hCG] and increase of testosterone production after hCG stimulation) evolved with the age of the horse. It is concluded that equine Leydig cells derive from two redundant successive postnatal generations and that there is no strict correlation between the functional properties and the morphological characteristics of these cells.

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.

Androgen binding protein, sperm production, semen output and LH and testosterone profiles in young postpubertal bulls

An androgen binding protein (ABP), which binds 5alpha-dihydrotestosterone with high affinity (Ka=0.3x10(9) M(-1)), has been demonstrated in testicular and epididymal cytosols of 5 young post pubertal bulls (15-17 months old) of the Montbeliarde dairy breed. Simultaneously, daily sperm production (DSP), semen output and plasma LH and testosterone concentrations (from frequent samplings) were determined. ABP levels were 21 fmoles/mg protein in testis and 59, 22 and 43 fmoles/mg, respectively, in caput, corpus and cauda epididymis. Mean DSP, per gram of testis, was 16.6x10(6) spermatozoa, and the mean sperm output was approximately 1.5x10(9) spermatozoa per ejaculate. Mean LH and testosterone levels were 1.5 ng/ml and 2.1 ng/ml, respectively. One bull (882) was clearly distinguishable from the others, in showing higher ABP and testosterone levels together with a lower daily sperm production. Results of this study may (1) suggest a physiological role of ABP in sperm epididymal maturation and (2) give a new parameter in the evaluation of individual bulls testicular function.

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.

In vitro pregnenolone metabolism by mouse adrenal gland: I-estrogen synthesis

Adrenal gland homogenates from four different strains of mice were incubated with (4-14C)-pregnenolone and a NADPH generating system. Although quantitative differences between high and low mammary tumor strains occured, all mice synthesized estrone. The highest aromatase activity was found 2 months after castration of the (C3H x RIII) F1 mice when castration was performed at 4 days of age; this activity was lower in the C3H mice and almost negligible in the RIII and C57BL mice.