Testosterone secretion during gubernacular development and testicular descent in the dog

Serum testosterone concentrations ranged from 0.24 to 1.45 nmol/l between Day 53 post coitum (p.c.) until Day 40 post partum (p.p.) and did not show variations that could be correlated with the process of testicular descent. The intratesticular androgen appeared to be mainly testosterone, its concentration being about 5000-fold higher than that in serum whereas 5 alpha-dihydrotestosterone could not be demonstrated. The intratesticular testosterone concentration at the initiation of gubernacular regression (Day 0) was apparently, but not significantly, higher than at Day 49 p.c. and at Day 40 p.p. The ability of the neonatal canine testis to synthesize testosterone was indicated by increased serum testosterone concentrations after hCG stimulation.     

Androgens in relation to prenatal development and postnatal inversion of the gubernacula in rats.

Exposure of male rats to the anti-androgen flutamide during fetal life, from day 10 after conception to the day of birth, allowed quantitatively unaltered development of the gubernacula. Apparently, androgens play no important role or no role at all in their growth. Castration of newborn male rats did not interfere with the inversion during further postnatal life of the gubernacula to create the muscular parts of the scrotum (cremaster muscles). Prenatal exposure to flutamide, followed by castration immediately after birth, also allowed gubernacular inversion and cremaster muscle growth. Neonatal administration of testosterone, after castration at birth, did not enhance gubernacular inversion or promote cremaster muscle growth in infancy or during adulthood. Apparently, postnatal gubernacular inversion and cremaster muscle growth are independent not only of androgens, but also of all testis hormones. Neonatal administration of the potent androgen 5 alpha-dihydrotestosterone propionate suppressed gonadotrophin secretion and, in intact males, inhibited testicular growth. Administration from the day of birth to day 33 delayed testicular descent and enhanced growth of the genital apparatus, but did not affect the size of the cremaster muscles. These experiments indicate that androgens are not involved in the processes that create the cavities into which testes descend to acquire their full reproductive potential.     

Role of adiponectin as a modulator of testicular function during aging in mice

The mechanisms by which testicular functions decline with aging remain largely speculative. Our recent finding showed the importance of adiponectin in the regulation of testicular functions, whereas its concentration declines during male infertility. Thus, the aim of present study was to explore the potential role of adiponectin during aging. The changes in adiponectin, adiponectin-receptors, and insulin receptor proteins expression in the testis were evaluated and compared with the testicular parameters, mass, and testosterone level in the mice from early post-natal to late senescence period. Further, the current study has examined the effect of exogenous adiponectin treatment on testicular functions in aged mice. The results showed a significant decline in adiponectin/adiponectin-receptors expression simultaneously with a significant decline in testicular mass, insulin receptor expression and testosterone synthesis in the testis of aged mice. Exogenous treatment of adiponectin to aged mice resulted in marked improvements in testicular mass, histological features (cells proliferation), insulin receptor expression, testicular glucose uptake, anti-oxidative enzymes activity and testosterone synthesis as compared with the control. Based on these findings, it may be concluded that a marked decline in adiponectin synthesis and action results in decreased insulin sensitivity (development of insulin resistance) and increased oxidative stress which consequently suppresses testicular functions during aging. This study further showed that treatment with adiponectin ameliorates reduced testicular functions by enhanced expression of insulin receptor in the testis of senescent mice. It is thus hypothesized that systemic adiponectin treatment could be a promising therapeutic strategy for improvement of testosterone production and sperm counts during aging.     

Cryptorchidism in mice with an androgen receptor ablation in gubernaculum testis

Androgens play a critical role in the development of the male reproductive system, including the positioning of the gonads. It is not clear, however, which developmental processes are influenced by androgens and what are the target tissues and cells mediating androgen signaling during testicular descent. Using a Cre-loxP approach, we have produced male mice (GU-ARKO) with conditional inactivation of the androgen receptor (Ar) gene in the gubernacular ligament connecting the epididymis to the caudal abdominal wall. The GU-ARKO males had normal testosterone levels but developed cryptorchidism with the testes located in a suprascrotal position. Although initially subfertile, the GU-ARKO males became sterile with age. We have shown that during development, the mutant gubernaculum failed to undergo eversion, a process giving rise to the processus vaginalis, a peritoneal outpouching inside the scrotum. As a result, the cremasteric sac did not form properly, and the testes remained in the low abdominal position. Abnormal development of the cremaster muscles in the GU-ARKO males suggested the participation of androgens in myogenic differentiation; however, males with conditional AR inactivation in the striated or smooth muscle cells had a normal testicular descent. Gene expression analysis showed that AR deficiency in GU-ARKO males led to the misexpression of genes involved in muscle differentiation, cell signaling, and extracellular space remodeling. We therefore conclude that AR signaling in gubernacular cells is required for gubernaculum eversion and outgrowth. The GU-ARKO mice provide a valuable model of isolated cryptorchidism, one of the most common birth defects in newborn boys.     

Effect of surgery and efferent duct ligation on testicular blood flow and testicular steroidogenesis in the rat

A moderate reduction in testicular blood flow was observed in both testes 24 h after unilateral efferent duct ligation without any corresponding change in testosterone secretion as indicated in the peripheral blood, in testicular venous blood, or in testicular tissue fluid. At 21 days a pronounced unilateral decrease in blood flow was associated with the extensive degeneration of tubules in the testis on the ligated side. These changes were also associated with decreased testosterone secretion by the testis on the ligated side, although Leydig cell function was not abolished since testosterone in the tissue increased rather than decreased. It is therefore concluded that testicular blood flow may play an important role in the changes of testosterone secretion that follow unilateral efferent duct ligation.     

Cryptorchidism: an indicator of testicular dysgenesis?

Cryptorchidism is a common ailment of new-born boys, affecting 1–9% of full term boys at birth. Cryptorchidism has been associated with an increased risk of testicular cancer and reduced fertility. Aetiology of cryptorchidism remains obscure in most cases. Familial occurrence suggests a heritable susceptibility to cryptorchidism; however, seasonal variation in the incidence of cryptorchidism suggests that environmental factors also contribute. Testicular descent is characterised by androgen-dependent regression of cranial suspensory ligament and androgen + insulin-like hormone 3 (Insl3)-dependent gubernacular outgrowth. Even though hormonal defects are rarely detected in patients, both hypo-and hypergonadotropic hormonal patterns have been associated with cryptorchidism. Moreover, cryptorchid boys have significantly reduced serum androgen bioactivity at 3 months of age when normal boys have a strong surge of reproductive hormones. Defects in Insl3 action cause cryptorchidism in male mice, and over-expression in female mice causes ovarian descent. Defects in leucine-rich repeat-containing G-protein-coupled receptor 8/G-protein-coupled receptor affecting testis descent (LGR8/GREAT), the receptor for Insl3, manifest the same phenotype as Insl3 knockout mutants. Even though mutations found in Insl3 and LGR8/GREAT genes are not a common cause of cryptorchidism in patients, it remains to be resolved whether low Insl3 levels during development are associated with cryptorchidism. Cryptorchidism may reflect foetal testicular dysgenesis that may later manifest as subfertility or testicular cancer.This work was supported by the Turku University Central Hospital, the Academy of Finland and the European Commission (contracts BMH4-CT96-0314, QLK4-CT1999-01422, QLK4-CT2001-00269 and QLK4-CT2002-00603).     

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.     

Müllerian inhibiting substance production and testicular migration and descent in the pouch young of a marsupial

The ontogeny of Müllerian inhibiting substance (MIS) production by the developing testis of an Australian marsupial, the tammar wallaby (Macropus eugenii), was determined during pouch life using an organ-culture bioassay of mouse fetal urogenital ridge. This information was related to the morphological events during testicular migration and descent. MIS biological activity was found in testes (but not ovaries or liver) of pouch young from 2 to 85 days of age. MIS production had commenced by day 2, which is within a day of the first gross morphological signs of testicular differentiation. Müllerian duct regression occurred between 10 and 30 days, which partly coincided with testicular migration to the inguinal region and enlargement of the gubernacular bulb (15 to 30 days). These observations are consistent with the hypothesis that MIS may be involved in testicular transabdominal migration. The epididymis commenced development and growth only after the testis had descended through the inguinal ring. This provides no support for the suggestion that the epididymis is involved in testicular descent into the scrotum. The basic sequence of events in post-testicular sexual differentiation in the wallaby is sufficiently similar to that seen in eutherian mammals to make it an excellent experimental model for future studies of testicular differentiation, migration and descent.     

Inhibitory effects of stress-activated nitric oxide on antioxidant enzymes and testicular steroidogenesis

The messenger role of nitric oxide (NO) in immobilization stress-induced inhibition of testicular steroidogenesis has been previously suggested. In accord with this, here, we show that the intratesticular injection of isosorbide dinitrate (ISDN; 2x2.5 mg/testis), an NO donor, mimicked the action of stress on serum testosterone concentrations and hCG-stimulated testosterone production in rat testicular tissue. When added in vitro, ISDN inhibited testicular 3beta-hydroxysteroid dehydrogenase and 17alpha-hydroxylase/lyase. Immobilization stress and injections of ISDN also decreased the activity of catalase, glutathione peroxidase, glutathione transferase, and glutathione reductase in the interstitial compartment of testis. When stressed rats were treated concomitantly with bilateral intratesticular injections of N(omega)-nitro-L-arginine methyl ester, a non-selective NOS inhibitor (2x600 microg/testis), the activities of antioxidative enzymes, as well as serum testosterone concentration, were partially normalized. These results indicate that stress-induced stimulation of the testicular NO signalling pathway leads to inhibition of both steroidogenic and antioxidant enzymes.     

Modulation of testicular functions by testicular opioid peptides.

The possible physiological role of testicular opioid peptides in the control of testicular functions has been studied. In neonatal rats intratesticular administration of opiate receptor antagonists (naloxone, nalmefene) stimulates Sertoli cell proliferation and secretion. Both in adult and neonatal rats local injection of the testis with opiate receptor antagonists or with beta-endorphin antiserum results in a decrease in steroidogenesis in long-term studies. Treatment of neonatal testis with an enkephalin analogue induces a short-term suppression of testosterone secretion. Further studies were carried out to investigate whether the above described local effects of opiate agonist or antagonist on testicular function are under the regulatory control of testicular nerves. Partial denervation of the testis was performed by testicular injection of 6-hydroxydopamine (a neurotoxin degenerating sympathetic neural structures) or by vasectomy (cutting the inferior spermatic nerve). If testicular administration of opioid agonist or antagonist was combined with partial denervation of the testis, the effects of pharmacological agents influencing testicular opioid level were not evident. The data indicate that opioid peptides synthesized in the testis are components of the intratesticular regulatory system and that local opioid actions are modulated by testicular nerves.     

Inverse relationship between testicular proliferation and apoptosis in mammalian seasonal breeders

Seasonal cycles of testicular activity occur in many mammals and can include transitions between total arrest and recrudescence of spermatogenesis. We hypothesize that involution and reactivation of testis result from two antagonistic processes, proliferation and programmed cell death (apoptosis), which are activated at different times. To test this hypothesis, quantitative measurements of both proliferation-specific marker and apoptotic produced nucleosomes have been compared with sperm and testosterone production in testes from adult roe deer during breeding and non-breeding seasons (May to September). Testes of brown hare were included from periods of testes regression (June to August) and recrudescence (November to December). The highest testicular weights in roe deer were found in the rutting period from late July to early August (27.25 +/- 8.56 g), corresponding with the highest number of testicular sperm/g parenchyma. The peak of sperm production coincided with a peak in testosterone concentration (1.19 +/- 0.53 microg/g testis). The maximum level of proliferation-specific marker was also found during the breeding season (98.6 +/- 58.2 U/g testis in comparison to 20.1 +/- 22.0 U/g in the prerutting period). In contrast, the most significant apoptosis was observed in the nonbreeding season than the breeding period (71.11 +/- 5.79 U/mg testis and 18.88 +/- 6.79 U/mg, respectively). Testicular proliferation was low in the brown hare (0.061 +/- 0.062 U/g) during involution of the testes. It was newly activated in November and December (0.85 +/- 0.33 U/g), preceding the increase in testicular volume. Testosterone production increased in conjunction with testicular proliferation. At this time, testicular apoptosis was significantly lower (14.16 +/- 2.12 U/mg testis) than during the period of pronounced testicular regression (30.16 +/- 19.95 U/g). These results suggest that regulation of seasonal testicular activity is characterized by an inverse relationship of proliferation and apoptosis.     

Suppression of insulin-like3 receptor reveals the role of β-catenin and Notch signaling in gubernaculum development

During male development, the testes move from a high intraabdominal position and descend into the scrotum. The gubernaculum, an inguinoscrotal ligament connecting the testis to the lower abdomen, is believed to play a critical role in this process. The first stage of testicular descent is controlled by insulin like3 hormone (INSL3), produced in testicular Leydig cells. Deletion of Insl3 or its receptor, Rxfp2, in mice causes cryptorchidism. We produced Cre/loxP regulated shRNA transgenic mice targeting RXFP2 expression. We have shown that the transgene was able to reduce Rxfp2 gene expression and thus behaved as a hypomorphic allele of Rxfp2. Variable degrees of uni- and bilateral cryptorchidism was detected in males with the activated shRNA transgene on an Rxfp2+/- background. Conditional suppression of Rxfp2 in the gubernaculum led to cryptorchidism. Gene expression analysis of a mutant cremasteric sac using Illumina microarrays indicated abnormal expression of a significant number of genes in Wnt/β-catenin and Notch pathways. We have demonstrated profound changes in the expression pattern of β-catenin, Notch1, desmin, and androgen receptor (AR), in Rxfp2-/- male embryos, indicating the role of INSL3 in proliferation, differentiation, and survival of specific cellular components of the gubernaculum. We have shown that INSL3/RXFP2 signaling is essential for myogenic differentiation and maintenance of AR-positive cells in the gubernaculum. Males with the deletion of β-catenin or Notch1 in the gubernacular ligament demonstrated abnormal development. Our data indicates that β-catenin and Notch pathways are potential targets of INSL3 signaling during gubernacular development.     

Limitations imposed by testicular blood flow on the function of Leydig cells in rats in vivo

Testis blood flow per testis closely follows testis weight in rats made aspermatogenic by a single exposure of the testis to 43 degrees C for 30 min or 500 rad (5 Gy) of irradiation from a caesium source, or following ligation of the efferent ducts. Aspermatogenesis following these treatments was associated with only minor changes in the concentrations of testosterone in peripheral blood before stimulation with human chorionic gonadotrophin (hCG), and a reduced responsiveness to hCG when testis weight had fallen after heating. The concentrations of testosterone in testicular venous blood was normal or above normal during aspermatogenesis resulting from heat or irradiation, and only slightly reduced following efferent duct ligation. Consequently testosterone production (defined as the product of plasma flow and the veno-arterial concentration difference for testosterone) was markedly reduced during aspermatogenesis, both before and after stimulation with hCG. It appears that the reduced blood flow limits the amount of testosterone leaving the testis, and while the Leydig cells are capable under some circumstances of compensating partially for this fall by increasing the concentration of testosterone in the testicular venous blood, this compensation is not complete when there are severe reductions in blood flow. Therefore one can conclude that the mass of the tubules is the main determinant of testis blood flow and the Leydig cells must manage with what the tubules require.     

Disturbed testicular descent in the rat after prenatal exposure to the antiandrogen flutamide.

Exposure of rats in utero to the anti-androgen flutamide resulted in feminization of the external genitalia that was noticeable at birth. This exposure also resulted in a high degree of cryptorchidism during adulthood. In most affected animals, testes were lying in 'ovary position' close to the caudal pole of the ipsilateral kidney. Cryptorchidism occurred despite normal prenatal development of the gubernacular cones and the transformation of these structures, postnatally, into muscular cremaster sacs. Inter- and intralitter variation in the response to prenatal exposure to flutamide was observed as well as intra-individual variation. Cryptorchidism frequently occurred unilaterally with right side cryptorchidism predominating. Cryptorchidism occurred in association with marked suppression of the growth of the ipsilateral epididymis and deferent duct. The possibility is considered that the poor development or absence of these structures contributes to cryptorchidism. Intra-individual variation supports the concept of the local nature of the influence of testis hormones in stabilization and further differentiation of the ipsilateral Wolffian duct derivatives. Cryptorchidism was enhanced when rats were treated postnatally with testosterone or oestradiol. The effect of testosterone was unexpected in view of the generally held hypothesis that androgens enhance testis descent. The effect of oestradiol was as expected: other animal models have been described in which induction of cryptorchidism by oestradiol occurs. Additional treatment with oestradiol caused further suppression of growth of the epididymis and deferent duct. The response to prenatal exposure to flutamide was not altered by further injections of flutamide postnatally. Such injections were without effect in males not exposed to flutamide prenatally except for minor, but statistically significant, testicular enlargement during adulthood. A model is thus presented that describes cryptorchidism as an endogenous developmental disorder.     

On the regulation of rat testicular steroidogenesis. Short term effect of luteinizing hormone and cycloheximide in vivo and Ca2+ in vitro on steroid production in cell-free systems.

An attempt has been made to correlate the rapid effect of luteinizing hormone on testicular steroid production in vivo with testicular steroid concentrations and in vitro steroid production rates in testis tissue preparations. Within 20 min after intravenous administration of 25 mug luteinizing hormone, increases were observed in testosterone concentrations in testicular venous plasma and in whole testis tissue and in pregnenlone concentrations isolated testis mitochondrial fractions. Testosterone production by whole testis homogenates and pregnenolone production by isolated mitochondrial fractions were significantly increased within 5 min after in vivo administration of luteinizing hormone. Injection of cycloheximide 10 min prior to luteinizing hormone prevented the stimulating effect of luteinizing hormone to steroid levels in testicular venous plasma and testis tissue and on steroid production rates by preparations of rat testis tissue. Cycloheximide treatment of control animals did not significantly alter testosterone concentrations and testosterone production rates vitro, although mitochondrial pregnenolone concentrations and production rates were decreased. Testosterone production by whole testis homogenates as well as the pregnenolone production by isolated mitochondrial fractions obtained from luteinizing hormone treated testes and control glands showed a biphasic time curve A period (5-10 min) of high steroid production was followed by a period lower steroid production. Addition of 25 mug luteinizing hormone or 10(-8)--10(-5) M adenosine 3':5'-monophosphate (cyclic AMP) to the incubation medium had no effect pregnenolone production by isolated mitochondrial fractions. Administration of leuteinizing hormone in vivo markedly enhance the stimulating effect of Ca2+ on testosterone production by whole testis homogenates and on pregnenolone production by isolated mitochondrial fractions.     

Regulation of steroidogenesis by atrial natriuretic peptide (ANP) in the rat testis: differential involvement of GC-A and C receptors

Previous studies have established a stimulatory effect of natriuretic peptides (NP) on testosterone production in mouse Leydig cells as intense as that of LH. Chronic administration of ANP in mice, on the other side, reduced testosterone levels. So, the understanding of the role of ANP on testicular steroidogenesis has been impaired by discrepant findings. The aim of the present study was to clarify the physiological role of ANP in the rat testis steroidogenesis using a model that preserves the interactions between testis cells and a medium devoid of any circulating factors that could interfere with testosterone production. First, ANP was immunolocalized in the interstitial compartment of the rat testis, mainly in Leydig cells. We also determined the presence of ANP and both GC-A (guanylyl cyclase A) and C receptors by real-time PCR in testis. Perfusion in vitro of testis with ANP (1 and 3x10(-7)M) stimulated testosterone production in a time- and dose-dependent manner. On the other side, testosterone secretion induced by LH was blunted by ANP. Similar effect was obtained using the specific C receptor ligand, cANF, indicating the involvement of C receptor in such response. In conclusion, ANP stimulated testosterone production in the rat testis perfused in vitro but decreased testosterone production LH-induced, effect that seems to involve C receptor. To this extent, our results suggest the existence of a local and complex peptidergic system in the rat testis, involving ANP and its receptors that could importantly modulate the androgen biosynthesis.     

Abnormalities of testicular descent

Testicular descent occurs in two stages. The transabdominal phase (8–15 weeks) is controlled by enlargement of the caudal genito-inguinal ligament (gubernaculum) and regression of the cranial ligament. Insulin-like 3 from the Leydig cell appears to be the prime stimulator of gubernacular growth, augmented by Müllerian inhibiting substance/anti-Müllerian hormone. Testosterone causes regression of the cranial ligament. The inguinoscrotal phase (25–35 weeks) requires the migration of the gubernaculum from the groin to the scrotum; this migration is guided by the genito-femoral nerve releasing calcitonin gene-related peptide under the influence of androgen. The neonatal gonocyte transforms into a type A spermatogonium at 3–12 months of age, a step that is now known to be crucial for subsequent fertility, as the stem cells for spermatogenesis are created in this structure. This step is blocked in undescended testis and, hence, orchidopexy is currently recommended at 6–12 months of age. Congenital cryptorchidism is caused by the failure of gubernacular migration to the scrotum (1%–2%) but we now recognise that another 1%–2% of boys have acquired cryptorchidism, secondary to the failure of spermatic cord elongation with growth of the boy. These latter cases come to operation at 5–10 years of age. Surgery remains the mainstay of treatment, as hormonal therapy has not been proven to be effective, presumably because testicular descent is a complex anatomical mechanism.     

Synthesis and aromatization of 19-norandrogens in the stallion testis

The results of the measurement of 19-nortestosterone in the testiscular artery and vein of the stallion, the very low levels of this steroid in the peripheral blood of geldings and the similar patterns of increase in the peripheral levels of 19-nortestosterone and testosterone after hCG stimulation, show that 19-nortestosterone, like testosterone, is essentially synthesized in the testis. This testicular origin was confirmed by the ability of testicular tissue to synthesize 19-norandrogens from [4-14C]androgens in vitro. 19-Nortestosterone was 50% conjugated in the peripheral blood and almost entirely conjugated after biosynthesis in vitro. The sequence of appearance of steroids in the peripheral blood after a single injection of 10,000 IU hCG suggests that, in the equine testis, 19-norandrogens are produced by a specific C10-19 desmolase (estrene synthetase), stimulable by hCG. 19-Nortestosterone was aromatized into estradiol-17 beta by stallion testicular microsomes. The affinity of the aromatase for 19-nortestosterone was very low compared to that for testosterone. At low and presumably physiological levels, and at a high testosterone/19-nortestosterone ratio, testosterone did not inhibit 19-nortestosterone aromatization by more than 53%. Thus, 19-nortestosterone may be aromatized in vivo in the testis in spite of the endogenous concentrations of androgens. However, the low velocity of 19-nortestosterone aromatization by testicular microsomes at roughly physiological concentrations suggests that 19-norandrogen aromatization may only participate slightly in the testicular estrogen production. These results suggest that in the equine testis, two aromatizing enzyme systems may exist: one which aromatizes both androgens and 19-norandrogens, and a minority system more specific for 19-norandrogens.     

Steroid metabolism in the gonads of a patient with testicular feminization. I. Metabolism of cholesterol, pregnenolone, progesterone and dehydroepiandrosterone in vitro.

The metabolism of cholesterol-4-14C, pregnenolone-4-14C, progesterone-4-14C and dehydroepiandrosterone-4-14C in a right abdominal and a left inguinal testis of a patient with testicular feminization was studied by a double isotope method in vitro. One of the main metabolites found in all incubations was testosterone. In incubations with cholesterol the delta4-pathway seems to be preferred. The rate of conversion of cholesterol to testosterone in the right testis was 1,27% and in the left testis 4,90%. Pregnenolone was converted to testosterone in the right testis at a rate of 6,61% and in the left testis at a rate of 3,23%. The conversion for testosterone using progesterone as precursor was 13,19% and 3,88% respectively and 11,97% of dehydroepiandrosterone was converted to testosterone in the right testis and 12,32% in the left testis. These findings are compared with data from the literature and conclusions are drawn.     

Inducible nitric oxide synthase in the rat testis: evidence for potential roles in both normal function and inflammation-mediated infertility

In vitro data have indicated that nitric oxide (NO) inhibits Leydig cell testosterone production, suggesting that NO may play a role in the suppression of steroidogenesis and spermatogenic function during inflammation. Consequently, we investigated expression of the inflammation-inducible isoform of NO synthase (iNOS) in the inflamed adult rat testis and the ability of a broad-spectrum inhibitor of NO production, L-nitro-L-arginine methyl ester, to prevent Leydig cell dysfunction during inflammation. Unexpectedly, immunohistochemical and mRNA data established that iNOS is expressed constitutively in Leydig cells and in a stage-specific manner in Sertoli, peritubular, and spermatogenic cells in the normal testis. Expression was increased in a dose-dependent manner in all these cell types during lipopolysaccharide (LPS)-induced inflammation. In noninflamed testes, treatment with the NO synthase inhibitor reduced testicular interstitial fluid formation and testosterone production without any effect on serum LH levels. Administration of the inhibitor did not prevent the suppression of testicular interstitial fluid and testosterone production that occurs within 6 h after LPS treatment. Collectively, these data indicate a novel role for iNOS in autocrine or paracrine regulation of the testicular vasculature, Leydig cell steroidogenesis, and spermatogenesis in the normal testis. The data suggest that increased NO is not the major cause of acute Leydig cell dysfunction in the LPS-treated inflammation model, although a role for NO in this process cannot be excluded, particularly at other time points. Moreover, up-regulation of iNOS may contribute to the seminiferous epithelium damage caused by LPS-induced inflammation.