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R M Sharpe

Publications and source records attributed to R M Sharpe.

At least 19 recordsLinked to original sources
PubMed1992

Stage-specific expression of rat transition protein 2 mRNA and possible localization to the chromatoid body of step 7 spermatids by in situ hybridization using a nonradioactive riboprobe.

The present study has used methoxyacetic acid (MAA)-induced depletion of specific germ cell types in the rat and in situ hybridization with nonradioactive riboprobes to determine the stages of the spermatogenic cycle at which there is expression of the mRNA for the basic chromosomal protein transition protein 2 (TP2). On Northern blots, an abundant mRNA was detectable in samples from control adult rats, but the amount of message was markedly reduced when RNA was extracted from the testes of rats treated 14 and 21 days previously with methoxyacetic acid. These testes were depleted specifically of step 7-12 spermatids, suggesting that these cells contain TP2 mRNA. When tissue sections were subjected to in situ hybridization, the TP2 mRNA was localized at the cellular and subcellular levels. Messenger RNA for TP2 was first detectable in spermatids at step 7. In these spermatids, at high magnification, in addition to some positive reaction in the cytoplasm, intense staining was located to a perinuclear structure consistent with localization of mRNA within the chromatoid body. The amount of TP2 mRNA in the cytoplasm increased as remodelling of the early spermatid nucleus progressed and was highest in step 10 and 11 spermatids at stages X and XI. Thereafter, the mRNA decreased until it was undetectable in step 14 spermatids at stage XIV. The localization of TP2 mRNA to the chromatoid body of step 7 spermatids would be consistent with this organelle being a storage site for long-lived mRNAs utilized later in spermiogenesis.

Animals↗
PubMed1992

Testosterone and FSH have independent, synergistic and stage-dependent effects upon spermatogenesis in the rat testis.

Adult rats were hypophysectomized and treated with ethane dimethanesulphonate (EDS) selectively to eliminate the Leydig cells in the testis. By removing the source of endogenous gonadotrophins and androgens, the subsequent effects on the seminiferous epithelium were studied after 20 days of treatment with vehicle, or FSH (2 x 50 micrograms/day) or a low dose of testosterone (0.6 mg testosterone esters every 3rd day) alone or in combination. Compared to vehicle-treated hypophysectomized rats with Leydig cells, testis weight in saline-treated hypophysectomized rats treated with EDS declined by 50%, spermatogenesis was disrupted severely and only 18% of the tubules contained spermatids, these being confined to stages I-VI of the spermatogenic cycle. Treatment with either FSH or testosterone esters alone significantly (P less than 0.01) increased testis weight compared to vehicle-treated hypophysectomized rats treated with EDS and 40% of tubules contained spermatids either at stages I-VI after FSH, or at all stages I-XIV after testosterone treatment. Treatment with FSH and testosterone esters together maintained testis weights approximately 20% above vehicle-treated hypophysectomized controls; over 70% of the seminiferous tubules contained spermatids and there was a marked stimulation of spermatogenesis at all stages of the spermatogenic cycle. The results suggest, that in the absence of the pituitary gland and the Leydig cells, FSH alone partially supports spermatogenesis up to the development of round spermatids whereas testosterone is capable of maintaining spermatid development at all 14 stages of the cycle. When FSH and testosterone were administered in combination, the effects upon spermatogenesis were far greater than the response expected if their individual effects were simply additive. It is therefore concluded that FSH may play a role in normal spermatogenesis and that this role is essentially that of augmenting the response of the testis to testosterone. The biochemical mechanisms via which this might occur are discussed and hypophysectomized rats treated with EDS used in the present studies should provide a useful approach for their identification.

Animals↗
PubMed1992

The role of specific germ cell types in modulation of the secretion of androgen-regulated proteins (ARPs) by stage VI-VIII seminiferous tubules from the adult rat.

This study has assessed the role of specific germ cell types in modulating the secretion of seven previously identified androgen-regulated proteins (ARPs) as well as the increase in overall level of protein secretion by seminiferous tubules (ST) at stages VI-VIII of the spermatogenic cycle in the rat. Methoxyacetic acid (MAA) was administered at 650 mg/kg to induce 80-100% depletion of pachytene and later spermatocytes; ST at stages VI-VIII were then isolated at 4, 18 and 30 days after MAA treatment when pachytene spermatocytes (PS), round spermatids (RS) or elongate spermatids (ES), respectively, were depleted selectively. By comparison with ST isolated from controls or from rats 4 days after ethanedimethane sulphonate (EDS)-induced testosterone withdrawal, the overall level of incorporation of 35S-methionine into ST-secreted proteins was assessed after culture for 22 h at 32 degrees C as well as the relative abundance of ARPs identified by two-dimensional sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Depletion of PS caused a substantial decrease in abundance of ARP-6 (53-57 kDa; pI 5.7-5.8) and ARP-7 (56-59 kDa; pI 5.9-6.2) and minor and more variable decreases in ARP-3 (27-30 kDa; pI 7.4) and ARP-4 (38 kDa; pI 6.0-6.2); ARP-6 and ARP-7 are comparable in size to the A and B forms of P-Mod-S, a product of the peritubular cells. Depletion of RS resulted in the complete disappearance of ARP-2 (13-14.5 kDa; pI 7.3-7.6), a decrease in abundance of ARP-7 and variable decreases in ARP-1 (approximately 9.5 kDa; pI 6.9-7.4) and ARP-6; ARP-1 and -2 are thought to be Sertoli cell-secreted proteins. Depletion of ES had no effect on secretion of the ARPs. Depletion of PS, RS or ES resulted in significant (P less than 0.001) decreases of 26, 38 and 42% respectively in the overall level of incorporation of methionine into ST-secreted proteins, but this was significantly less than the decrease (55%) induced by EDS-induced testosterone withdrawal. These results show that the androgen-dependent changes in secretion of proteins, which occur specifically at stages VI-VIII of the normal spermatogenic cycle, are largely, if not completely, dependent on a normal germ cell complement, with each germ cell type regulating the secretion of proteins essential for its own development.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetates↗
PubMed1992

Evaluation of the role of germ cells in regulating the route of secretion of immunoactive inhibin from the rat testis.

During normal sexual maturation of the male rat there is a progressive change in the route of secretion of inhibin by the Sertoli cell, from a predominantly basal route of secretion in prepuberty to a predominantly apical route of secretion in adulthood. This change may be monitored by comparing the levels of inhibin in testicular (TV), spermatic and peripheral (PV) venous blood and the levels in testicular interstitial fluid (IF). This study has assessed the role of germ cells in effecting this change by assessing (a) the effect of total germ cell depletion by X-irradiation of the males in utero, and (b) the effect of selective germ cell depletion in adulthood using the testicular toxicant, methoxyacetic acid (MAA). Female rats were X-irradiated on day 20 of gestation to produce male offspring whose testes were germ-cell deficient. Blood and IF samples were collected from groups of these offspring and age-matched controls at 35 and 100 days of age. In blood and IF samples, inhibin concentrations were significantly higher at 35 days of age than at 100 days. The absence of germ cells in X-irradiated animals did not affect the age-related fall in inhibin levels, nor the change in the predominant route of secretion of inhibin from the testis into blood. Testosterone was almost undetectable in 35-day-old controls, but was raised significantly by 100 days of age. In X-irradiated animals, testosterone levels were increased significantly at 35 days of age, and the levels in most samples were increased even more substantially by 100 days of age. However, PV levels of testosterone in 100-day-old X-irradiated animals were significantly lower than in controls. LH and FSH levels were raised in X-irradiated animals compared with their age-matched controls, but FSH levels in X-irradiated animals still fell with age, as in the controls. The role of specific germ cell types in regulating the route of secretion of inhibin from the normal adult testis was studied after depletion (80-100%) of pachytene and later spermatocytes by a single oral administration of MAA (650 mg/kg) to adult rats. At 3 days after MAA treatment, coincident with the loss of pachytene spermatocytes, plasma inhibin levels were increased significantly in blood and IF samples, and this was associated with a dramatic change in the route of secretion of inhibin from the testis, with increased secretion of this peptide via the base of the Sertoli cell into IF and TV blood.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Evaluation of changes in the secretion of immunoactive inhibin by adult rat seminiferous tubules in vitro as an indicator of early toxicant action on spermatogenesis.

A method for culturing isolated seminiferous tubules (ST) from adult rats for 1-3 days has been developed and optimized rigorously on the basis of the secretion of immunoactive inhibin under basal conditions and after maximal stimulation with rat FSH or dibutyryl cyclic AMP. The effect on these cultures of three known testicular toxicants was assessed. Of these, two are thought to act on the Sertoli cell, meta-dinitrobenzene (mDNB) and nitrobenzene (NB), while the third, methoxy acetic acid (MAA), is thought to act on pachytene spermatocytes. In addition, the effect of a possible testicular toxicant, 3-mononitrotoluene (3-MNT), was investigated. These data were compared with those obtained using cultures of immature rat Sertoli cells (SC) or SC + germ cells and with data on the effect of equivalent doses of the compounds on the secretion of immunoactive inhibin in vivo. In studies designed to optimize conditions for the secretion of immunoactive inhibin by ST in culture, significant effects were found of the type of culture medium used, the duration of culture, the total and individual length of tubules used, etc. All subsequent studies with toxicants utilized optimal conditions. Addition of either mDNB or NB to ST cultures at 10(-5) or 10(-3) M, or MAA at 10(-4) M, stimulated basal secretion of immunoactive inhibin by two- to fourfold on Days 1, 2, or 3 of culture while FSH or dibutyryl cyclic AMP-stimulated secretion of immunoactive inhibin was either unaffected or was enhanced to a small extent. At the same doses, mDNB or NB also enhanced secretion of immunoactive inhibin by SC cultures. although these effects were more variable and of smaller magnitude than the effects on ST cultures. In contrast, addition of up to 10(-3) MAA to cocultures of SC + germ cells had no effect on the secretion of immunoactive inhibin. Exposure of rats in vivo to levels of mDNB, NB, or MAA similar to those which stimulated secretion of immunoactive inhibin in vitro resulted in a two- to fourfold increase in the levels of immunoactive inhibin in testicular interstitial fluid (IF) at 1 and 3 days post-treatment, and this was associated with early impairment of spermatogenesis (as judged by testis weight). In contrast to these effects, addition of 3-MNT to ST or SC cultures had no effect except at 10(-3) M, when the secretion of immunoactive inhibin was increased marginally.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetates↗
PubMed1991

Evidence that secretion of immunoactive inhibin by seminiferous tubules from the adult rat testis is regulated by specific germ cell types: correlation between in vivo and in vitro studies.

This study has assessed whether depletion of specific germ cell types is able to alter the secretion of immunoactive inhibin by adult Sertoli cells in vivo and in vitro. Pachytene and later spermatocytes were depleted (80-100%) by a single administration of methoxy acetic acid (MAA; 650 mg/kg) to adult rats. At intervals between 1 and 42 days posttreatment, rats were killed, and the blood levels of FSH, LH, and testosterone were determined together with the levels of immunoactive inhibin in plasma and testicular interstitial fluid (IF). At the same time intervals, seminiferous tubules (ST; 5 x 2 cm) were isolated from control and MAA-treated rats and cultured for 24-72 h in the presence or absence of rat FSH, (Bu)2cAMP, or MAA under rigorously optimized conditions. The hormonal changes observed were related to the presence/absence of specific germ cell types, as determined by assessment of testicular morphology in perfusion-fixed testes from similarly treated rats. One to 3 days after MAA treatment, coincident with the depletion of pachytene spermatocytes, blood levels of FSH were increased significantly compared with controls; FSH returned to control levels at 7-14 days (when early spermatids were depleted), but were increased again at 21-35 days (when late spermatids were depleted). In contrast, while the plasma levels of immunoactive inhibin were increased 2-fold 3 days posttreatment, they were comparable to controls at 7-14 days, but were decreased substantially at 21-28 days. The levels of immunoactive inhibin in testicular IF were more than doubled 1 and 3 days posttreatment, but were comparable to control levels at all other times. Blood levels of LH showed a similar pattern of change to FSH, although only at 21-28 days after MAA treatment was there a significant increase, while blood levels of testosterone were comparable at all times in control and MAA-treated rats. To confirm that the changes observed in vivo after MAA treatment were indicative of changes in Sertoli rather than Leydig cell secretion of immonoactive inhibin, its secretion by isolated ST was assessed, and a pattern of change similar to that in plasma was observed. Thus, when cultured for 24 h under basal conditions, ST from rats 1-3 days after MAA treatment showed a 2- to 3-fold increase in secretion of immunoactive inhibin, which returned to control levels at 7-14 days before being reduced substantially at 21-28 days and then recovering to control levels; similar changes were observed for FSH- and (Bu)2cAMP-stimulated secretion of immunoactive inhibin.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetates↗
PubMed1991

Evidence for the control of testicular interstitial fluid volume in the rat by specific germ cell types.

Following on from our recent evidence that Sertoli cells may regulate testicular interstitial fluid (IF) volume, this study has assessed whether depletion of specific germ cell types in vivo is associated with changes in recovered IF volume. Germ cell depletion was induced by either a single oral administration of 650 mg methoxyacetic acid (MAA)/kg or exposure of the testes to local heating (43 degrees C for 30 min). Treatment with MAA induced depletion or loss of most pachytene and later spermatocytes at 1-3 days and, because of maturation depletion, this resulted in the specific depletion of later germ cell types at 7-35 days. Testicular IF volume was unchanged at 1-7 days after MAA treatment but was increased significantly (P less than 0.01) at 14 days and was nearly doubled (P less than 0.001) at 21 days, before returning to control levels at 28-42 days. Serum LH (and FSH) levels were generally higher in MAA-treated rats, especially at 21 and 28 days, but there was no obvious correlation between LH levels and IF volume changes. Similarly, there was no relationship between IF volume changes and testicular weight or IF levels of testosterone. The increase in IF volume at 14-21 days after MAA treatment coincided with specific depletion of the later elongate spermatids (steps 14-19) and, when these cells reappeared in the testis, IF volume normalized. This possible causal association was studied further in rats exposed to local testicular heating which, within 3 days, caused major depletion of pachytene spermatocytes and early (step 1-8) spermatids.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1991

[Germ cells and post-natal development of testicular function: in vitro studies].

Studies in recent years have clearly established that, in addition to the well known endocrine regulation by gonadotrophin hormones, spermatogenesis is under the modulatory control of a complex set of paracrine regulators. Whereas the role of Leydig cells (testosterone) and of Sertoli cells (nurce cells of germ cells) in spermatogenesis has focused most of the attention, until recently little was known about the contribution of germ cells in the spermatogenetic process. This was the aim of the present experiments. We have used, in vitro, 3 complementary approaches; 1) we measured the influence of the removal of germ cells contaminating Sertoli cell cultures by a hypotonic treatment; 2) in coculture, we examined to what extend isolated germ cells could affect Sertoli cell function; 3) we investigated the effects of germ cell conditioned media on Sertoli cell cultures. Our results indicate that germ cells are able to modulate Sertoli cell function in vitro. This germ cell influence varies according to: 1) the germ cell fraction tested (pachytene spermatocytes, early spermatids or cytoplast from elongated spermatids/residual bodies); 2) the parameter of Sertoli cell function studied (inhibition of oestradiol; stimulation of androgen-binding protein, transferrin...); 3) the age of the Sertoli cell donors; 4) the hormonal environment (+/- FSH). Furthermore we wave demonstrated that germ cell effects were partly at least mediated via proteinaceous factor(s) detected in germ cell spent media. Taking into account previous in vivo studies and these in vitro results, we have hypothesized that germ cells, in conjunction with hormones (LH, FSH, testosterone) play an important role in the ontogenesis of Sertoli cells and therefore in spermatogenesis.

Androgen-Binding Protein↗
PubMed1990

Regulation of Sertoli cell inhibin production and of inhibin alpha-subunit mRNA levels by specific germ cell types.

To elucidate the endocrine and paracrine regulation of testicular inhibin production, the effects of follicle-stimulating hormone (FSH), (Bu)2cAMP, germ cells (either crude or enriched preparations) and germ cell-conditioned media on inhibin production (immuno- and bio-activities) and the levels of alpha- and beta B-subunit mRNAs were assessed in cultured Sertoli cells isolated from 20-day-old rats. FSH and (Bu)2-cAMP stimulated both secreted and intracellular inhibin levels in a dose-dependent manner. Using cDNA probes corresponding to the alpha-subunit and the beta B-subunit of rat inhibin it was also shown that both FSH and (Bu)2cAMP markedly increased the level of alpha-subunit mRNA but had no effect on the beta B-subunit mRNA. Addition of a crude mixture of germ cells to Sertoli cell monolayers was found to enhance inhibin secretion. Of the different germ cell fractions tested in co-culture, early spermatids reproducibly stimulated both basal and (Bu)2cAMP-induced production of inhibin whereas pachytene spermatocytes only increased the latter; cytoplasts from elongated spermatids (CES) had no effect. Co-culture of Sertoli cells with liver epithelial cells (LEC) significantly enhanced (Bu)2cAMP-induced inhibin levels. Media conditioned by early spermatids consistently and dramatically stimulated the secretion of both bioactive and immunoactive inhibin by Sertoli cells while spent media from pachytene spermatocytes displayed less activity. CES-conditioned media had only minor stimulatory effects, which may have resulted from the contamination of this fraction by spermatids. Media conditioned by LEC had no effect on inhibin production, confirming that the activity of this cell line is not mediated via a diffusible factor. Early spermatids were found to increase levels of the alpha-subunit mRNA. The current study provides evidence for the involvement of germ cells, in particular of early spermatids, in the local testicular regulation of inhibin gene expression and production in the rat. This may be of crucial importance for the ontogeny of this parameter of Sertoli cell function, and has important implications with regard to the postulated endocrine and paracrine roles of inhibin.

Animals↗
PubMed1990

Cell-cell interactions in the control of spermatogenesis as studied using Leydig cell destruction and testosterone replacement.

This review centers around studies which have used ethane dimethane sulphonate (EDS) selectively to destroy all of the Leydig cells in the adult rat testis. With additional manipulations such as testosterone replacement and/or experimental induction of severe seminiferous tubule damage in EDS-injected rats, the following questions have been addressed: 1) What are the roles and relative importance of testosterone and other non-androgenic Leydig cell products in normal spermatogenesis and testicular function in general? 2) What are the factors controlling Leydig cell proliferation and maturation? 3) Is it the Leydig cells or the seminiferous tubules (or both) which control the testicular vasculature? The findings emphasize that in the normal adult rat testis there is a complex interaction between the Leydig cells, the Sertoli (and/or peritubular) cells, the germ cells, and the vasculature, and that testosterone, but not other Leydig cell products, plays a central role in many of these interactions. The Leydig cells drive spermatogenesis via the secretion of testosterone which acts on the Sertoli and/or peritubular cells to create an environment which enables normal progression of germ cells through stage VII of the spermatogenic cycle. In addition, testosterone is involved in the control of the vasculature, and hence the formation of testicular interstitial fluid, presumably again via effects on the Sertoli and/or peritubular cells. When Leydig cells regenerate and mature after their destruction by EDS, it can be shown that both the rate and the location of regenerating Leydig cells is determined by an interplay between endocrine (LH and perhaps FSH) and paracrine factors; the latter emanate from the seminiferous tubules and are determined by the germ cell complement. Taken together with other data on the paracrine control of Leydig cell testosterone secretion by the seminiferous tubules, these findings demonstrate that the functions of all of the cell types in the testis are interwoven in a highly organized manner. This has considerable implications with regard to the concentration of research effort on in vitro studies of the testis, and is discussed together with the need for a multidisciplinary approach if the complex control of spermatogenesis is ever to be properly understood.

Animals↗
PubMed1990

Changes in Sertoli cell function in vitro induced by nitrobenzene.

Nitrobenzene (NB) has been identified as a testicular toxicant in vivo, but its site of action remains unknown. In the present study, the effect of NB on the Sertoli cell was assessed in vitro using Sertoli cell and Sertoli-germ cell cocultures. The parameters measured were the exfoliation of germ cells; the secretion of lactate, pyruvate, and inhibin; and gross cellular morphology. The effect of metadinitrobenzene (mDNB), a related compound which is a known Sertoli cell toxicant, was assessed for comparison. Gross morphological changes including vacuolation of Sertoli cells were observed following treatment of cultures with 10(-3) M NB. Exposure of cocultures to NB also resulted in dose-dependent exfoliation of predominantly viable germ cells. NB (greater than 5 X 10(-4) M) and mDNB at the single dose level used (10(-4) M) stimulated the secretion of lactate and pyruvate significantly by Sertoli cells, an effect that was more marked in the absence of germ cells. Comparable changes were observed in follicle stimulating hormone (FSH)-stimulated cultures. Inhibin secretion by Sertoli cells was also altered by exposure to NB but in a biphasic manner, with low (10(-8) to 10(-6) M) and high (10(-4) to 10(-3) M) doses enhancing inhibin secretion while intermediate (10(-5) M) doses had no effect. These effects were evident in both culture systems but inhibin secretion by Sertoli-germ cell cocultures was always greater than that by Sertoli cell cultures. However, these effects of NB on inhibin secretion were not evident in FSH-stimulated cultures. In contrast to the effects of NB, mDNB had no effect on basal secretion of inhibin but blocked the stimulatory effect of FSH. It is concluded that NB, like mDNB, is probably a Sertoli cell toxicant in view of its similar disruptive effects on various parameters of Sertoli cell function. However, NB is far less toxic than mDNB at equivalent concentrations in vitro. The present study is the first to evaluate the potential of inhibin secretion by Sertoli cells in culture as an additional marker of toxicant action, and concludes that it merits further study in this context.

Animals↗
PubMed1990

The levels and possible involvement of leukotriene B4 and prostaglandin F2 alpha in the control of interstitial fluid volume in the rat testis.

The possible involvement of two arachidonic acid metabolites, prostaglandin F2 alpha (PGF2 alpha) and leukotriene B4 (LTB4), in the stimulatory effect of human chorionic gonadotrophin (hCG) on the volume of interstitial fluid (IF) in the rat testis has been investigated. Administration of hCG caused a time- and dose-dependent increase in the IF levels of PGF2 alpha while LTB4 showed no clear dose-dependence, but did decrease significantly at 2-8 h after injection of 100 IU hCG. Administration of ethane dimethane sulphonate (EDS), which specifically destroys Leydig cells, decreased the volume of IF but the IF levels of LTB4 and PGF2 alpha were unchanged. This indicates that although the absence of Leydig cells results in significant changes in IF volume, LTB4 and PGF2 alpha are probably not involved in these changes. Furthermore, these findings suggest that Leydig cells are not the only contributors to LTB4 and prostaglandins E2 and F2 alpha in testicular IF. In rats injected peripherally with hCG, intratesticular administration of the cycloxygenase inhibitor, indomethacin, decreased PGF2 alpha levels in IF after 2 and 4 h but not at later times. However, no inhibitory effect of indomethacin on the hCG-stimulated increase in IF volume was detected; indeed, at 2 h after injection of indomethacin + hCG there was a significant increase in IF volume in the indomethacin-injected testis. It is concluded that, although prostaglandins and LTB4 are secreted into IF in the rat testis, these arachidonic acid metabolites are apparently not the primary mediators of the increase in IF volume that follows hCG treatment.

Analysis of Variance↗
PubMed1990

The effects of sexual maturation and altered steroid synthesis on the production and route of secretion of inhibin-alpha from the rat testis.

This study has determined the route of secretion of inhibin-alpha into blood by the rat testis during sexual maturation, and in adult animals in which Leydig cell steroidogenesis was stimulated with human CG (hCG) or suppressed with aminoglutethimide. In each rat, inhibin-alpha levels were measured in samples of testicular (TV), spermatic (SV), and peripheral (PV) venous blood plasma, and in testicular interstitial fluid (IF). The IF and TV plasma reflect inhibin-alpha secretion via the base of the Sertoli cell while that secreted via the apex of the Sertoli cell (which is resorbed from the rete testis) was determined from the difference between SV and TV levels of inhibin-alpha. During sexual maturation, inhibin-alpha levels in IF and all plasma samples declined from maximal values at 28 days of age to minimal values at 100 days of age, in contrast to testosterone levels which showed the reverse pattern. There was a major change with age in the route of secretion of inhibin-alpha from the testis into blood. In immature (28-35 days) rats, most inhibin-alpha (58-65%) leaving the testis in blood was derived from that secreted via the base of the Sertoli cell with a relatively small contribution (35-42%) from apically-secreted inhibin-alpha. However, the latter made a progressively increasing contribution between 45 and 100 days of age (adults) and in adult rats the vast majority of inhibin-alpha (95%) leaving the testis in blood was derived from apically-secreted inhibin-alpha. This change was due primarily to a progressive reduction with age in the secretion of inhibin-alpha via the base of the Sertoli cell, a change which was confirmed by inhibin bioassay. Stimulation of steroidogenesis in the adult testis with hCG significantly increased inhibin-alpha and testosterone levels in IF and all plasma samples. The concomitant administration of hCG and aminoglutethimide (to block steroidogenesis) prevented the hCG-induced increase in testosterone levels, but still led to significant increases in inhibin-alpha secretion which were comparable to those seen with the use of hCG alone. The administration of aminoglutethimide (AMG) on its own did not alter the inhibin-alpha secretion profile from that seen in controls, but it did significantly reduce the levels of testosterone in all fluids. In rats treated with hCG +/- AMG there was a small change in the route of secretion of inhibin-alpha into blood, with an increased contribution (24-37%) from inhibin-alpha secreted via the base of the Sertoli cell, when compared with controls (7-16%).(ABSTRACT TRUNCATED AT 400 WORDS)

Aminoglutethimide↗
PubMed1986

Macrophages in the interstitial tissue of the rat testis.

Macrophages were identified in the intertubular tissue of the rat testis by loading animals with a particulate vital dye (trypan blue or India ink) and by localizing immunocytochemically a macrophage membrane antigen (MRC W3/25). Leydig cells were identified by the histochemical staining reaction for 3 beta-hydroxysteroid dehydrogenase activity and by a monoclonal antibody. Macrophages were scattered in the interstitial tissue closely attached to and mixed with the Leydig cells. They were never found in the seminiferous tubules. The macrophages comprised about 25% of all the cells in the interstitium. Double staining with a vital dye and a marker antibody showed that all the phagocytosing cells were macrophages and that the Leydig cells did not take up vital dyes. Double staining for the demonstration of the 3 beta-hydroxysteroid dehydrogenase activity and the macrophage antigen likewise revealed two distinctly different cell populations. Crude Leydig cell preparations obtained by collagenase treatment of the testis contained macrophages (12-14%). Macrophages were present throughout the postnatal prepuberal development of the testis. Their density was increased in the cryptorchid and irradiated testis.

3-Hydroxysteroid Dehydrogenases↗
PubMed1979

The effect of induced hyperprolactinaemia on Leydig cell function and LH-induced loss of LH-receptors in the rat testis.

Anterior pituitary glands were transplanted beneath the kidney capsule of intact, adult male rats to induce hyperprolactinaemia. This resulted in reduced serum levels of LH and FSH and increased adrenal weight. In pituitary-transplanted rats, testicular hCG-receptor binding was increased by 55 to 175%, whilst the capacity of the testis to secrete testosterone in vitro was greatly reduced. Injection of ovine LH into control and pituitary-transplanted rats resulted in similar percentage reductions in hCG-receptor binding in the two groups. This treatment impaired the in vitro steroidogenic responsiveness of testes from control rats at 24 h after injection, but had no major effect on the already-impaired, steroidogenic responsiveness of testes from pituitary-transplanted rats. Although induction of hyperprolactinaemia resulted in marked changes in Leydig cell function, these alterations were possibly due to the chronically reduced serum gonadotrophin levels in hyperprolactinaemic rats as well as a direct effect of prolactin on the Leydig cell.

Animals↗