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PubMed2003

Pdgfr-alpha mediates testis cord organization and fetal Leydig cell development in the XY gonad.

During testis development, the rapid morphological changes initiated by Sry require the coordinate integration of many signaling pathways. Based on the established role of the platelet-derived growth factor (PDGF) family of ligands and receptors in migration, proliferation, and differentiation of cells in various organ systems, we have investigated the role of PDGF in testis organogenesis. Analysis of expression patterns and characterization of the gonad phenotype in Pdgfr-alpha(-/-) embryos identified PDGFR-alpha as a critical mediator of signaling in the early testis at multiple steps of testis development. Pdgfr-alpha(-/-) XY gonads displayed disruptions in the organization of the vasculature and in the partitioning of interstitial and testis cord compartments. Closer examination revealed severe reductions in characteristic XY proliferation, mesonephric cell migration, and fetal Leydig cell differentiation. This work identifies PDGF signaling through the alpha receptor as an important event downstream of Sry in testis organogenesis and Leydig cell differentiation.

Animals↗
PubMed1983

In vitro metabolism of progesterone by the human undescended testis.

Testicular biopsy specimens from 28 boys with undescended testis, and from 6 men operated post-pubertally for undescended testis, were incubated in vitro with [3H]progesterone (P). Significant steroid metabolic activity was demonstrated in all biopsies. Before puberty the total conversion rate was low and only a small amount of 17 alpha-hydroxy-progesterone (17 alpha-OH-P) was formed. The amount of newly formed 20 alpha-dihydro-progesterone (20 alpha-DH-P) was relatively constant regardless of increasing maturity. After puberty the total conversion rate was higher. More 17 alpha-OH-P was synthesized, and the ratio between formed 20 alpha-DH-P and 17 alpha-OH-P decreased significantly. The position of the undescended testis did not appear to influence progesterone metabolism. In no case could we demonstrate deficient steroidogenesis. In one 17-year old boy the 20 alpha-DH-P/17 alpha-OH-P ratio was lower in the undescended testis (0.9) than in the scrotal testis (4.0) suggesting increased steroidogenesis per mg tissue in the malpositioned testis. The indication from the present study, that even grossly displaced testes have a relatively undisturbed steroidogenic capability, suggests that the reason for impaired descent may not simply reflect disturbed androgen synthesis, but must involve other mechanisms.

Adolescent↗
PubMed1987

Morphometric analysis of the components of the neonatal and the adult rat testis interstitium.

Leydig cells in the foetal rat testis are still present at birth and it has been hypothesized that they commence to degenerate immediately after birth, based on the decrease in their volume density (v/v%) with age. In this study the interstitium of the rat testis was studied quantitatively at 1, 5, 10, 15, 20 and 90 days after birth: the latter are considered to be adults. The absolute volumes of connective tissue cells and blood vessels increased with age. The absolute volumes of macrophages and lymphatic spaces were greater at 90 days than at any other age. The absolute volume of foetal Leydig cells per testis was unchanged from 1 to 15 days, despite a decrease in the % volume occupied per testis. The number of foetal Leydig cells per testis did not decline from days 1-20 although on day 20 an average foetal Leydig cell was smaller in volume than at earlier ages (days 1-15). Adult Leydig cells were recognized at day 10 and their absolute volume and number per testis increased from 15 to 90 days. Adult Leydig cells were similar in morphology to foetal Leydig cells at 20 days except for a reduced volume of cytoplasmic lipid.

Animals↗
PubMed1988

Inhibition of growth and differentiation of fetal hamster gonads grafted into the adult testis.

A cytomorphological analysis of the effect of adult testes on growth and differentiation of grafted fetal testis or ovaries was performed in hamsters. Fetal gonads, taken at 14 days post-coital age, were grafted for 30 days either under the renal capsule or testicular capsule of scrotal or cryptorchid testes of adult hamsters (weight 115 +/- 23 g). Renal grafts were also performed in males castrated 30 days prior to receiving the fetal gonads. Growth and differentiation of the fetal gonads (testis or ovary) was totally inhibited by the scrotal testis. When the cryptorchid testis was the recipient of fetal gonads, inhibition was correlated inversely with the degree of spermatogenic damage elicited in the cryptorchid testis. No inhibition was observed in fetal gonads grafted under the kidney capsule, nor in castrated, normal or cryptorchid animals. As normal growth and differentiation of both testis and ovary occurred when grafted under the kidney capsule, the inhibitory effect of adult gonads seems to be unrelated to plasma testosterone levels in the host, as levels were undetectable in castrated hamsters and reduced drastically in cryptorchid animals. At the same time, the testicular-inhibiting substance in normal animals did not act at a distance, since its effect was restricted to fetal gonads grafted under the testicular capsule. This inhibitory substance may correspond to the spermatogonial chalone, known to be produced by differentiating spermatogenic cells (mainly spermatocytes and round spermatids in the rat and mouse); these chalones prevent spermatogonial proliferation and, consequently, the critical number of spermatogonia needed to enter meiosis is not attained. It is doubtful if the same substance has the ability to differentiate the fetal ovary or if this effect can be ascribed to a more complex situation involving other testicular peptides of paracrine action and/or locally high levels of androgens.

Animals↗
PubMed2004

Ontogenesis and cell specific localization of Fas ligand expression in the rat testis.

Over the past few years, a number of experimental evidences suggested the involvement of Fas Ligand (FasL) expressing Sertoli cells to induce apoptosis of Fas bearing germ cells. However, the FasL expression during testicular development and its cell specific localization within the testis is still a matter of debate. In the present study, we have monitored FasL expression during rat testis development by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and evaluated cell specific localization of FasL expression, by in situ RT-PCR and immunohistochemistry, on adult rat testis. RT-PCR analysis, performed on total RNA from rat testes obtained from 1 day up to 1-year-old animals, demonstrated the presence of FasL transcripts at all developmental stages examined. In situ RT-PCR analysis clearly indicated the presence of FasL mRNA in Sertoli cells of adult testis, while we could never detect FasL transcripts in germ cells. Immunohistochemistry experiments showed a strong immunostaining for FasL in Sertoli cells of adult testis and again, no immunopositivity was observed in germ cells. In conclusion, our data suggest that FasL expression in rat testis is present from the early postnatal days up to the adult, and the Sertoli cells is the main FasL expressing cell within the seminiferous tubule.

Aging↗
PubMedDate not supplied

Studies on the male antifertility agent--gossypol acetic acid. III. Effect of gossypol acetic acid on rat testis.

Gossypol acetic acid at the dose of 5 mg/rat/day for 2 and 4 weeks did not cause any significant effect on the body weight, testis, epididymis, seminal vesicle and prostate weight, nor gossypol treatment had any significant effect on the activities of acid phosphatase and succinic dehydrogenase in the testis. Changes in the testis ATPase activity were, however, significant after gossypol treatment. During the course of present investigations no effect of gossypol treatment on 3H thymidine incorporation into DNA of testicular cells was observed, nor there were any changes in the DNA and total protein content of the testis after gossypol treatment. Gossypol treatment did not cause any effect on the plasma Na+ level. However, transient decrease in the plasma K+ level was observed; decrease in K+ level two weeks after gossypol treatment was restored to normal after 4 weeks of gossypol treatment. No changes in the histology of the testis were observed 2 weeks after gossypol treatment but marked inhibition of spermatogenesis was observed 4 weeks after gossypol treatment. Motility of vas deferens spermatozoa was also markedly inhibited 4 weeks after gossypol treatment. In the light of the present observations and those of others, there is a clear demonstration that gossypol acts directly on the spermatozoa and on the testis; at both the sites the drug interferes in the ATPase activity.

Adenosine Triphosphatases↗
PubMed2006

The testis in immune privilege.

The production, differentiation, and presence of male gametes represent inimitable challenges to the immune system, as they are unique to the body and appear long after the maturation of the immune system and formation of systemic self-tolerance. Known to protect germ cells and foreign tissue grafts from autoimmune attack, the 'immune privilege' of the testis was originally, and somewhat simplistically, attributed to the existence of the blood-testis barrier. Recent research has shown a previously unknown level of complexity with a multitude of factors, both physical and immunological, necessary for the establishment and maintenance of the immunotolerance in the testis. Besides the blood-testis barrier and a diminished capability of the large testicular resident macrophage population to mount an inflammatory response, it is the constitutive expression of anti-inflammatory cytokines in the testis by immune and particularly somatic cells, that represents an essential element for local immunosuppression. The role of androgens in testicular immune regulation has long been underestimated; yet, accumulating evidence now shows that they orchestrate the inhibition of proinflammatory cytokine expression and shift cytokine balance toward a tolerogenic environment. Furthermore, the role of the testicular dendritic cells in suppressing antigen-specific immunity and T-lymphocyte activation is discussed. Finally, the active role mast cells play in the induction and amplification of immune responses, both in infertile humans and in experimental models, highlights the importance of preventing mast cell activation to maintain the immune-privileged status of the testis.

Animals↗
PubMed1991

Evaluation of the impression technique by measuring interstitial oedema in rat testis.

The impression method for assessment of subcutaneous oedema was evaluated in a rat testis model where the testicular interstitial fluid volume was changed both artificially by infusion of rat plasma and pharmacologically by administration of human chorionic gonadotrophin. Both the integral value and the impression force value, as measured with the impression method, changed with infused volume, and changes as small as 16 microliters (approximately 7% of the total interstitial fluid volume in a testis) could be detected. Rats were treated with a single injection of 100 i.u. human chorionic gonadotrophin in order to induce changes in the volume of interstitial fluid in the testis. Both the integral value and the impression force value seemed to reveal information on testicular interstitial fluid volume in rats treated with human chorionic gonadotrophin that was similar to data revealed by measuring the actual fluid content in the testis. Interstitial fluid volume measured morphometrically in the contralateral testis in human chorionic gonadotrophin-treated rats was significantly correlated to the impression force value (r = 0.75) and the integral value (r = 0.52). This rat testis model proved to be an interesting experimental set-up for evaluation of the impression technique.

Animals↗
PubMed1993

A novel 205-kilodalton testis-specific serine/threonine protein kinase associated with microtubules of the spermatid manchette.

To identify proteins which interact with and potentially modulate the function of microtubules during spermatogenesis, we prepared a total testis MAP (microtubule-associated protein) antiserum and used it to isolate cDNA clones from a mouse testis cDNA expression library. Antibodies affinity purified by using one expression clone recognized a 205-kDa protein, termed MAST205, which colocalizes with the spermatid manchette. Sequencing of full-length cDNA clones encoding MAST205 revealed it to be a novel serine/threonine kinase with a catalytic domain related to those of the A and C families. The testis-specific MAST205 RNA increases in abundance during prepuberal testis development, peaking at the spermatid stage. The microtubule-binding region of MAST205 occupies a central region of the molecule including the kinase domain and sequences C terminal to this domain. Binding of MAST205 to microtubules requires interaction with other MAPs, since it does not bind to MAP-free tubulin. A 75-kDa protein associated with immunoprecipitates of MAST205 from extracts of both whole testis and testis microtubules becomes phosphorylated in in vitro kinase assays. This 75-kDa substrate of the MAST205 kinase may form part of the MAST205 protein complex which binds microtubules. The MAST205 protein complex may function to link the signal transduction pathway with the organization of manchette microtubules.

Amino Acid Sequence↗
PubMed1996

Segregation analysis of the testis-determining autosomal trait, Tda, that differs between the C57Bl/6J and DBA/2J mouse strains suggests a multigenic threshold model.

The testis-determining autosomal trait (Tda) of the mouse was uncovered when the Y chromosome of the poschiavinus variety of Mus musculus domesticus was introduced into the C57BL/6J laboratory strain background. Testis development is normal in the F1 generation but, in the backcross and subsequent crosses to C57BL/6J females, XY individuals with the poschiavinus Y chromosome expressed bilateral ovaries or various combinations of an ovotestis with a contralateral ovary or testis or bilateral ovotestes and few had testes bilaterally. In other strain backgrounds, such as DBA/2J, XY individuals with the poschiavinus Y chromosome always expressed normal testes bilaterally. The first breeding analysis of this difference in the interaction of strain background with the poschiavinus Y chromosome suggested that the Tda trait was due to a single gene, but attempts to map it failed. We constructed two strains of C57BL/6J and DBA/2J that are consomic for the poschiavinus Y chromosome in order to conduct a segregation analysis of the Tda trait. In the C57BL/6J.Y-POS consomic strain, liability to express incomplete testis development is normally distributed and thresholds in development specify the probability of different classes of ovary, ovotestis, and testis combinations. Testis development is complete in the DBA/2J.Y-POS consomic strain. We demonstrated previously that the Tda trait of C57BL/6J is recessive to that of DBA/2J and the segregating first backcross generation of embryos rejected the single-gene model. We have extended our analysis to a F2 generation of embryos that also rejects a single-gene model. We also report a test mating analysis of the first backcross generation. It was initiated to provide an independent assessment of the single-gene model, but the analysis of the distribution of test mating results suggests that the difference in the Tda trait between C57BL/6J and DBA/2J may be due to a small number of loci, possibly four or five, and that the phenotypic effect between loci may be additive.

Animals↗
PubMed2006

A novel cancer testis antigen that is frequently expressed in pancreatic, lung, and endometrial cancers.

PURPOSE: To isolate cancer testis antigens that are expressed in pancreatic cancers and may be useful in clinical applications. EXPERIMENTAL DESIGN: To efficiently isolate cancer testis antigens, a testis cDNA library was immunoscreened (SEREX) with serum from a patient with pancreatic ductal adenocarcinoma. The expression of isolated antigens in various cancer cell lines and tissues was evaluated by reverse transcription-PCR and Northern blot analyses. The immunogenicity of the antigen in cancer patients was evaluated by detection of the IgG antibody in sera from patients with various cancers. RESULTS: Of the three clones isolated through screening of a total of 2 x 10(6) cDNA library clones, one clone (KU-CT-1) was found to be expressed in various cancers but only in testis among normal tissues, indicating that it was a novel cancer testis antigen. The KU-CT-1 gene is located on chromosome 10p12 and produces two splice variants, which encode proteins of 397 and 872 amino acids, respectively. KU-CT-1 was expressed in pancreatic cancer tissues (3 of 9, 33%), lung cancer tissues (9 of 24, 38%), and endometrial cancer tissues (7 of 11, 64%). Specific serum IgG antibodies were detected in 3 of 20 pancreatic cancer patients, 2 of 12 endometrial cancer patients, 1 of 18 colon cancer patients, and 1 of 10 prostate cancer patients but not detected in 30 healthy individuals. CONCLUSIONS: KU-CT-1 is a new cancer testis antigen that is expressed in pancreatic, lung, and endometrial cancers and may be useful for diagnosis and immunotherapy for patients with various cancers.

Amino Acid Sequence↗
PubMed2003

In silico analysis indicates a similar gene expression pattern between human brain and testis.

OBJECTIVES: Previous data has reported similarity between human brain and testis gene expression patterns. Brain is the most important tissue in human speciation. Hence, it means that human testis could also play a crucial role in human speciation if these two tissues exhibit similar gene expression patterns. However, previous reports were based on only limited and scattered data. Determining the large scale anatomy of gene expression patterns of various human tissues could draw a more convincing conclusion, and better our understanding of the correlation/inter-correlation among different tissues. Furthermore, it could also provide a clue for evolutionary study. METHODS: To obtain gene expression information for large-scale data analysis, expression data of 760 Unigenes in seventeen human tissues (liver, lung, testis, brain, ovary, uterus, colon, stomach, heart, eye, kidney, spleen, gall bladder, breast, thymus, prostate and pancreas) were retrieved by DDD (differential digital display) analysis, and this expression data was subjected to clustering analysis. These Unigenes represent a wide range of genes classified according to their characterization and function. RESULTS: Among the 17 tissues, the highest similarity in gene expression patterns was between human brain and testis, based on DDD and clustering analysis. Genes contributing to the similarity include ribosomal protein (RP) genes as well as genes involved in transcription, translation and cell division. CONCLUSIONS: Present results provide evidence to support the proposal that human testis and brain share the highest similarity of gene expression patterns. The implications of the similarity regarding that both brain and testis contributed to human speciation are discussed.

Brain↗
PubMed1996

Apoptosis in adult mouse testis induced by experimental cryptorchidism.

Induction of cryptorchidism in the mouse causes infertility due to disruption of spermatogenesis including reduction of germ cells; however, the cellular mechanism responsible for the degenerative changes in cryptorchid testis is still unclear. In surgically induced bilateral cryptorchidism of 3-month-old C57BL/Tw mice, cellular changes in the cryptorchid testis were studied 1, 2, 3, 7, 14 and 21 days after the operation by electron microscopy, DNA fragmentation, in situ 3'-end labeling, serum and testicular testosterone measurements and gene expression. Although the testis showed DNA fragmentation even in intact mice, the cryptorchidism increased the degree of the fragmentation at 1 postcryptorchidism (p.c.) day. Apoptosis was encountered mainly in spermatids and spermatocytes. The number of apoptotic cells in the cryptorchid testis showed a 7-fold increase at 1 p.c day as compared to the intact testis, then it gradually decreased. Serum testosterone levels showed a significant decrease at 2 p.c. days and remained low thereafter. Expression of transforming growth factor-beta 2 (TGF-beta 2), TGF-beta 3, tumor necrosis factor-alpha receptor and Fas mRNAs increased in the cryptorchid testis within 24 h after the operation. In lpr(cg) and lpr mice lacking functional Fas, gld mice lacking functional Fas ligand and lpr(cg)-gld mice lacking both functional Fas and Fas ligand, the experimental cryptorchidism also induced apoptosis in germ cells at 1 p.c. day. The present results indicate that cryptorchidism induces apoptotic dell death in germ cells, and that testosterone reduction and the Fas system may not be significantly involved in the apoptosis of male germ cells.

Animals↗
PubMed1997

Autonomic innervation of the bovine testis.

The autonomic nerve supply of the bovine testis is investigated in animals of different ages by means of immunohistochemistry. Staining with antiserum to protein gene product 9.5 gives the most complete results for the study of the general innervation pattern. Autonomic nerves reach the testis by three different routes: with the blood vessels of the spermatic cord (funicular nervous contribution), by the mesorchium (mesorchial nervous contribution) and by the ligamentous bridge between epididymal tail and testis (caudal nervous contribution). The vessels of the spermatic cord are densely innervated. The large vessels of the vascular layer within the tunica albuginea display a discontinuous innervation pattern. In the interior of the testis, the caudal half of the gonad is completely free of any innervation. Slight differences in arrangement and fiber composition of testicular nerves in calves and bulls point to a reduction of the innervation with advancing age. The vast majority of bovine testicular nerves are dopamine-beta-hydroxylase-positive postganglionic sympathetic axons with vasomotor function. There is no evidence for a cholinergic innervation of the bovine testis. About half of the bovine testicular nerves are neuropeptide Y-immunoreactive. In the adult, solitary calcitonin gene-related peptide-immunoreactive fibers are the only ones independent of blood vessels. The absence of an innervation in the caudal half of the testis underlines the importance of local factors and blood-borne substances for the regulation of intratesticular blood flow in the bovine.

Aging↗
PubMed2005

The thymus is similar to the testis in its pattern of circadian clock gene expression.

The molecular basis for the circadian clock in mammals consists of a number of genes and proteins that form transcription-translation feedback loops. These loops result in a 24-h rhythm in the expression of mRNA and protein levels. Although the anatomical site of the central circadian clock is the SCN of the hypothalamus, all of the circadian clock genes are expressed in tissues other than the brain. Moreover, cyclic gene and protein expression occurs in most of these tissues. The best known exception to this rule is the testis, which shows constant rather than cyclic expression of circadian clock genes. Indeed, the testis of multiple animal species displays constant circadian clock gene expression. In recent work, the authors showed that the thymus is similar to the testis in that expression of circadian clock genes is either constant over a 24-h period or cycles with a dampened amplitude, depending on which gene is examined. In the current study, they extend and confirm their findings regarding noncyclic circadian clock gene and protein expression in the testis and the thymus. More important, they also show that expression of these genes in both testis and thymus does not depend on the transcriptional activator, CLOCK, which is necessary for cyclic gene expression in the SCN and in other tissues. These results extend the molecular similarities between the thymus and the testis and suggest that similar mechanisms are at work for regulating expression of circadian clock genes in both tissues. One commonality between these 2 organs is that they are composed primarily of differentiating cells. The authors hypothesize that the circadian clock is not operational in immature, differentiating cells. Possibly, the clock starts in mature cells upon receipt of an initiating signal.

Animals↗
PubMed2004

The role of tumor necrosis factor-alpha and interleukin-1 in the mammalian testis and their involvement in testicular torsion and autoimmune orchitis.

This review will focus the roles of TNF-alpha, IL-1 alpha, and IL-1 beta in the mammalian testis and in two testicular pathologies, testicular torsion and orchitis. TNF alpha in the testis is produced by round spermatids, pachytene spermatocytes, and testicular macrophages. The type 1 TNF receptor has been found on Sertoli and Leydig cells and numerous studies suggest a paracrine mode of action for TNF alpha in the normal testis. IL-1 alpha has been reported to be produced by Sertoli cells, testicular macrophages, and possibly postmeiotic germ cells. IL-1 receptors have been reported on Sertoli cells, Leydig cells, testicular macrophages, and germ cells suggesting both autocrine and paracrine functions. While these proinflammatory cytokines have important roles in normal testicular homeostasis, an elevation of their expression can lead to testicular dysfunctions. Testicular torsion is a clinical pathology with results in testicular ischemia and surgical intervention is often required for reperfusion. A pivotal role for IL-1beta in the pathology of testicular torsion has been recently described whereby an increase in IL-1beta production after reperfusion of the testis is correlated with the activation of the stress-related kinase, c-jun N-terminal kinase, and ultimately resulting in neutrophil recruitment to the testis and germ cell apoptosis. In autoimmune orchitis, on the other hand, TNF alpha produced by T-lymphocytes and macrophages of the testis has been implicated in the development and progression of the disease. Thus, both proinflammatory cytokines, TNF alpha and IL-1, have significant roles in normal testicular functions as well as in certain testicular pathologies.

Animals↗
PubMed2005

Testis structure and function in a nongenetic hyperadipose rat model at prepubertal and adult ages.

There are few data for hormonal levels and testis structure and function during postnatal development in rats neonatally treated with monosodium L-glutamate (MSG). In our study, newborn male pups were ip injected with MSG (4 mg/g body weight) every 2 d up to 10 d of age and investigated at prepubertal and adult ages. Plasma levels of leptin, LH, FSH, prolactin, testosterone (T), corticosterone, and free T4 (FT4) were measured. MSG rats displayed elevated circulating levels of corticosterone and hyperadiposity/hyperleptinemia, regardless of the age examined; conversely, circulating prolactin levels were not affected. Moreover, prepubertal MSG rats revealed a significant (P < 0.05) reduction in testis weight and the number of Sertoli (SC) and Leydig cells per testis. Leptin plasma levels were severalfold higher (2.41 vs. 8.07; P < 0.05) in prepubertal MSG rats, and these animals displayed plasma LH, FSH, T, and FT4 levels significantly decreased (P < 0.05). Taken together, these data indicate that testis development, as well as SC and Leydig cell proliferation, were disturbed in prepubertal MSG rats. Adult MSG rats also displayed significantly higher leptin plasma levels (7.26 vs. 27.04; P < 0.05) and lower (P < 0.05) LH and FSH plasma levels. However, T and FT4 plasma levels were normal, and no apparent alterations were observed in testis structure of MSG rats. Only the number of SCs per testis was significantly (P < 0.05) reduced in the adult MSG rats. In conclusion, although early installed hyperadipose/hyperleptinemia phenotype was probably responsible for the reproductive axis damages in MSG animals, it remains to be investigated whether this condition is the main factor for hypothalamus-pituitary-gonadal axis dysfunction in MSG rats.

Adipose Tissue↗
PubMed1984

Ontogeny of gonadotropin receptors in the fetal and neonatal rat testis.

To evaluate the extent to which LH receptors may participate in the regulation of testosterone production by the fetal and neonatal rat testis, the gonadal content of LH receptors was determined and correlated with the gonadal content of testosterone and other steroids at daily intervals throughout the period of sexual differentiation and early neonatal life. Also, to determine if FSH has a potential role during fetal life, FSH receptors were measured from 14.5 until 21.5 days of gestation, just before birth. LH receptors were first detected in the fetal rat testis at 15.5 days of gestation, at a concentration of 0.072 +/- 0.016 fmol/gonad. This is the time at which previous studies have shown a biological response to LH stimulation with increases in cAMP and testosterone production. LH receptor content remained constant from 15.5-17.5 days of gestation and then increased sharply at 18.5 days of gestation to 0.706 +/- 0.046 fmol/gonad, coincident with a surge in the testosterone content of the fetal testis. LH receptor content continued to rise until birth, reaching a maximum level of 2.00 +/- 0.24 fmol/gonad at 21.5 days of gestation, and did not significantly differ from this value through 5 days after birth, whereas intratesticular testosterone content decreased after birth. FSH receptors could be measured from 17.5 days of gestation, but remained very low through 19.5 days of fetal life. At 20.5 days, FSH receptor levels began to rise sharply and continued to increase through 21.5 days of gestation, just before birth. These data show that LH receptors are measurable at the time when the fetal testis becomes responsive to LH stimulation. It is possible that the increase in LH receptors may act as a mechanism for amplification of the stimulatory effect of low circulating LH levels on the fetal testis being concomitant with the intratesticular testosterone increase at the same stage. The decrease in testosterone production after birth cannot be attributed to a decrease in LH receptors in the neonatal gonad. Since 5 alpha-reduced androgens increase after birth, other possibilities, such as alternative steroid pathways, are a more likely explanation for the decrease in testosterone content. The presence of FSH receptors in the fetal testis imply that this hormone may have a function in the developing gonad, particularly in the last 2 days of fetal life.

Aging↗