Testosterone and androstanediol production by regenerating Leydig cells in the ethylene dimethane sulphonate-treated mature rat

Loss of hamster Leydig cells during regression after exposure to a short photoperiod

The aim of the present study was to evaluate the changes that occur in hamster Leydig cells during regression. Animals were divided into control, mild regression (MR), strong regression (SR) and total regression (TR) groups. Leydig cells were characterised by light and electron microscopy. Terminal deoxyribonucleotidyl transferase-mediated dUTP–digoxigenin nick end-labelling (TUNEL) and proliferating cell nuclear antigen (PCNA) antibodies were used to detect apoptosis and proliferation respectively. Three types of Leydig cells (A, B and C) could be differentiated. Type A cells were small in size compared with Leydig cells from animals exposed to a long photoperiod, which was a result of a decreased cytoplasm and nucleus. Type B cells were even smaller than Type A cells in regression groups. Type C exhibited cytoplasm vacuolisation. The percentage of Type C cells from the control group was much lower than in the MR, SR and TR groups. (P < 0.05). In the SR and TR groups, there was a significant decrease in the percentage of Type B cells compared with the control and MR groups (P < 0.05). The total number of Leydig cells decreased during testicular regression (P < 0.05). The total number of Type A and B cells was significantly lower in the MR, SR and TR groups compared with the control group (P < 0.05). There were no significant differences in the proliferation and apoptosis index in the groups studied. The findings of the present study indicate that there are three types of Leydig cells (A, B and C) in all hamsters studied and that regression causes an increase in the number of Type C cells, so that the reduction in the number Leydig cells during the phases of regression studied must be the result of necrosis and/or necroptosis.

Cellular changes in the hamster testicular interstitium with ageing and after exposure to short photoperiod

The aim of this study was to evaluate the cellular changes that occur in the hamster testicular interstitium in two very different physiological situations involving testicular involution: ageing and exposure to a short photoperiod. The animals were divided into an ‘age group’ with three subgroups – young, adult and old animals – and a ‘regressed group’ with animals subjected to a short photoperiod. The testicular interstitium was characterised by light and electron microscopy. Interstitial cells were studied histochemically with regard to their proliferation, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP in situ nick end labelling (TUNEL+) and testosterone synthetic activity. We identified two types of Leydig cell: Type A cells showed a normal morphology, while Type B cells appeared necrotic. With ageing, pericyte proliferation decreased but there was no variation in the index of TUNEL-positive Leydig cells. In the regressed group, pericyte proliferation was greater and TUNEL-positive cells were not observed in the interstitium. The testicular interstitium suffered few ultrastructural changes during ageing and necrotic Leydig cells were observed. In contrast, an ultrastructural involution of Leydig cells with no necrosis was observed in the regressed group. In conclusion, the testicular interstitium of Mesocricetus auratus showed different cellular changes in the two groups (age and regressed), probably due to the irreversible nature of ageing and the reversible character of changes induced by short photoperiod.

Developmental exposures of male rats to soy isoflavones impact Leydig cell differentiation

Testicular Leydig cells, which are the predominant source of the male sex steroid hormone testosterone, express estrogen receptors (ESRs) and are subject to regulation by estrogen. Following ingestion, the two major isoflavones in soybeans, genistin and daidzin, are hydrolyzed by gut microflora to form genistein and daidzein, which have the capacity to bind ESRs and affect gene expression. Thus, the increasing use of soy-based products as nondairy sources of protein has raised concerns about the potential of these products to cause reproductive toxicity. In the present study, perinatal exposure of male rats to isoflavones induced proliferative activity in Leydig cells. Isoflavones have the capacity to act directly as mitogens in Leydig cells, because genistein treatment induced Leydig cell division in vitro. Genistein action regulating Leydig cell division involved ESRs, acting in concert with signaling molecules in the transduction pathway mediated by protein kinase B (AKT) and mitogen-activated protein kinase (MAPK). Enhanced proliferative activity in the prepubertal period increased Leydig cell numbers, which alleviated deficits in androgen biosynthesis and/or augmented serum and testicular testosterone concentrations in adulthood. Together, these observations indicate that the perinatal exposures of male rats to isoflavones affected Leydig cell differentiation, and they imply that including soy products in the diets of neonates has potential implications for testis function.

The potential roles of estrogens in regulating Leydig cell development and function: a review

It is generally agreed that estrogens, principally estradiol-17beta, are synthesized by and act in the testis of mammals, including humans. The site of estradiol synthesis in the testis is generally believed to begin in the Sertoli cell and switch to the Leydig cell during neonatal development where a gonadotropin-regulated aromatase is present. Numerous studies suggest that the primary target cell of estradiol in the testis at all ages is the Leydig cell. In fact, the Leydig cell is known to possess an estrogen receptor that binds estradiol in the classic manner. The mechanism of estradiol action and the role of its receptor in the testis, however, remain unresolved. In Leydig cells, estradiol appears to induce several alterations that are dependent in large part on the developmental stage of the Leydig cell. In the fetal and neonatal testes, estradiol appears to block the ontogenic development of Leydig cells from precursor cells. There is also evidence that estradiol similarly blocks the regeneration of Leydig cells in the testis of mature, ethane dimethylsulfonate-treated animals. Evidence indicates that the precursor cell possesses high levels of estrogen receptors relative to that of the Leydig cell. It is postulated that estradiol is a paracrine factor involved in regulating the interstitial population of Leydig cells. Evidence also indicates that estradiol acts directly in the mature testis to block androgen production. It appears to do so by inhibiting the activities of several steroidogenic enzymes involved in testosterone synthesis. Although the more conventional receptor-mediated mode of action is feasible, several studies have suggested that this action might entail direct competitive inhibition of key steroidogenic enzymes by estradiol. In summary, the net biologic effect of estradiol in the testis appears to be inhibition of androgen production, either by limiting development and growth of the Leydig cell population or through direct action in the Leydig cell.

hCG-induced changes in LH/CG receptor mRNA transcript levels in the testis of adult hypophysectomized, ethane dimethyl sulphonate-treated rats

To elucidate the molecular mechanisms involved in the development of precursor cells into functional Leydig cells, effects of hCG on the expression of the luteinizing hormone (LH)/chorionic gonadotrophin (CG) receptor gene were investigated in the testis of adult hypophysectomized, ethane dimethyl sulphonate (EDS)-treated rats. The alkylating drug EDS specifically destroys Leydig cells in the adult rat testis. In hypophysectomized rats, in the absence of LH, this is not followed by the formation of new Leydig cells, leaving a testis in which Leydig cell precursors are presumed to be the only cell type that possess LH receptors. The absence of Leydig cells was confirmed by determining the gene expression of two key steroidogenic enzymes, 3 beta-hydroxysteroid dehydrogenase/isomerase (3 beta HSD) and P-450 17 alpha-hydroxylase/C17-20 lyase (P-45017 alpha) in these animals. Northern blot analysis revealed that hypophysectomy, followed by EDS treatment decreased the total amount of LH/CG receptor mRNA and drastically changed the pattern of LH/CG receptor mRNA transcripts. In the testis of intact adult rats, the expression of the LH/CG receptor gene results in multiple mRNA transcripts with molecular sizes of approximately 7.0, 4.2, 2.5, 1.8 and 1.2 kb. The most abundant species observed in the testis of adult hypophysectomized, EDS-treated rats was the 1.8 kb mRNA transcript, whereas the levels of the other mRNA transcripts were decreased. To stimulate the development of precursor cells into functional Leydig cells, hypophysectomized, EDS-treated rats were treated with high doses of hCG (100 IU) for different periods of time.(ABSTRACT TRUNCATED AT 250 WORDS)

Steroidogenic enzyme activity in the hypogonadal (hpg) mouse testis and effect of treatment with luteinizing hormone

The hypogonadal (hpg) mouse, which lacks circulating gonadotrophins during development, has been used (a) to determine whether initial expression of steroidogenic enzyme activity is dependent upon gonadotrophins and (b) to examine the responsiveness of these enzymes to luteinizing hormone (LH) stimulation. Activities of 17 alpha-hydroxylase, 17-ketosteroid reductase and 5 alpha-reductase were very low but detectable in the hpg testis while cholesterol side-chain cleavage (CSCC) activity was undetectable. In contrast, 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) activity was high (11% of normal testis). Treatment with LH increased CSCC and 17 alpha-hydroxylase activity more than 11-fold within 24 h. 5 alpha-Reductase activity was increased 3-fold after 3 days treatment while 17-ketosteroid reductase and 3 beta HSD activities did not respond until after 10 days of treatment. The overall increases in 5 alpha-reductase (4-fold) and 3 beta HSD (6-fold) activities were low while changes in 17-ketosteroid reductase (20-fold) and, particularly, CSCC (greater than 130-fold) and 17 alpha-hydroxylase (153-fold) were more marked. Results show (1) that expression of 3 beta HSD activity may be independent of gonadotrophins, (2) that activity of 17 alpha-hydroxylase, 17-ketosteroid reductase and 5 alpha-reductase is expressed, though at low levels, in the absence of gonadotrophins and (3) that prior exposure to gonadotrophins is not required for a rapid response to LH stimulation, particularly with respect to the cytochrome P-450 enzymes.

Immature rat Leydig cells are intrinsically less sensitive than adult Leydig cells to ethane dimethanesulfonate

Leydig cells from immature rat testes appear to be insensitive to doses of ethane-1,2-dimethanesulfonate (EDS) which eliminate Leydig cells from adult rat testes. We sought to determine whether this differential response to EDS is intrinsic to the Leydig cell or mediated by other intra- or extratesticular differences between adult and immature rats. To differentiate among these possibilities, Leydig cells were exposed to EDS (1) in vivo, (2) through in vitro testicular perfusion, or (3) in highly purified Leydig cell primary cultures. Four days after ip injections of 85 mg EDS/kg body wt Leydig cells were eliminated from testes of adult, but not immature rats. Total androgen production by testes perfused in vitro with 94 micrograms EDS/ml was dramatically reduced in adult, but not immature rats. Highly purified adult, but not immature, rat Leydig cells were far more sensitive to the effects of EDS on luteinizing hormone-stimulated androgen production (functional effects; apparent EC50 = 94 for adult and 407 micrograms/ml for immature rat Leydig cells) and on [35S]methionine incorporation (cytotoxic effects; apparent EC50 = 140 for adult and 1000 micrograms/ml for immature rat Leydig cells). Finally, the in vitro effects of EDS were both cell type and chemical specific. Since the differential response of adult and immature rat Leydig cells to EDS was manifest in vivo, during in vitro testicular perfusion, and in highly purified Leydig cell primary cultures, we conclude that immature rat Leydig cells are intrinsically less sensitive to the specific cytotoxic effects of EDS than adult rat Leydig cells.

Interstitial cell proliferation in the testis of the ethylene dimethane sulfonate-treated rat

This study was conducted to examine interstitial cell proliferation in the testis of the ethylene dimethane sulfonate (EDS)-treated rat. Initial autoradiographic studies demonstrated a peak of [3H]thymidine incorporation by interstitial cells at 2 and 4 days post-EDS treatment. Subsequent studies were designed using in vivo pulse labeling regimens in an attempt to identify interstitial cell proliferation associated with Leydig cell regeneration. Rats were injected with [3H]thymidine at days 2 and 4 post-EDS and were killed 6 hours later or at 30 days post-EDS. Although cells labeled at 2 and 4 days post-EDS appeared to undergo subsequent division, the Leydig cells visible at 30 days post-EDS were not labeled. In a second study, rats were injected with [3H]thymidine at days 10 and 20 post-EDS and were killed either 6 hours later or at 24 days post-EDS. In the 10-day post-EDS group, interstitial cells were labeled at both the 6-hour and 24-day time points; however, Leydig cells present at 24 days were not labeled. In contrast, the testes of rats that were killed at 20 days post-EDS (6 hours labeling period) contained Leydig cells that displayed grains over the nucleus, thus suggesting that Leydig cell proliferation had occurred. In addition, a high number of the Leydig cells observed at 24 days post-EDS were labeled, suggesting that they arose from divisions occurring during the 20- to 24-day post-EDS period. These studies demonstrate that interstitial cell proliferation occurs in several stages following EDS treatment.(ABSTRACT TRUNCATED AT 250 WORDS)