Androgen-binding Protein Secretion Research Articles

Maternal exposure to PM2.5 disrupting offspring spermatogenesis through induced sertoli cells apoptosis via inhibin B hypermethylation in mice

Particulate Matter 2.5 (PM2.5) disrupts endocrine functions and may negatively affect sperm quality and quantity in males; however, the long-term effects and potential mechanisms of this effect are unknown. This study aimed to investigate the epigenetic mechanism of maternal exposure to PM2.5-induced inhibin B hypermethylation in male offspring. In this experiment design, pregnant C57BL/6 mice were treated with two doses of PM2.5 (4.8 and 43.2 mg/kg bw). The membrane control group was given a sampling membrane and the control group received nothing. Following the formation of the vaginal plug, intratracheal instillation of PM2.5 was administered every three days until delivery of the pups. To assess the effect of PM2.5 in vitro, TM4 cells, a Sertoli-like cell line, was treated with different concentrations (0, 25, 50, 100 μg/mL) of PM2.5 for 24 h. The results displayed that Sperm motility, as well as the number of adult offspring, was decreased in the PM2.5 exposed group relative to the untreated controls. Increased vacuolization was observed in the Sertoli cells of mice that were exposed to PM2.5 in utero. The levels of inhibin and testosterone were reduced and the levels of LH and FSH increased in the PM2.5 groups relative to the untreated controls. In vitro, PM2.5 resulted in cell cycle inhibition as well as increased apoptosis in TM4 cells. Moreover, PM2.5-induced inhibin B hypermethylation and activation of the p21/Cleaved Caspase-3 pathway resulted in TM4 cell apoptosis that was rescued through the use of a DNA methylation inhibitor. Together, our data suggest that prenatal exposure to PM2.5 results in inhibin B hypermethylation and can activate the p21/Cleaved Caspase-3 pathway, resulting in Sertoli cell apoptosis, aberrant secretion of androgen binding protein, and decreased testosterone, thus resulting in the inhibition of spermatogenesis.

The Sertoli cell: Novel clinical potentiality.

The Sertoli cell is important for endocrine and paracrine control of spermatogenesis. Functions attributed to Sertoli cells are: (1) supportive and trophic functions for the cells of the seminiferous epithelium, (2) transport of mature spermatids towards the lumen of seminiferous tubules, (3) secretion of androgen binding protein, (4) production of substances with endocrine or paracrine action for spermatogenesis control and (5) interaction with intertubular endocrine Leydig cells. Inhibin B and anti-Müllerian hormone (AMH) are glycoproteins belonging to the transforming growth factor β (TGF-β) superfamily; they are produced almost exclusively by the Sertoli cells and have been proposed as direct markers of their function and indirect markers of spermatogenesis. Serum inhibin B and AMH concentrations seem to constitute additional diagnostic parameters in male subfertility as they reflect Sertoli cell function. Stimulated concentrations of serum inhibin B and AMH do not add clinically relevant information in subfertile men compared to basal concentrations of these hormones. Serum inhibin B and AMH concentrations correlate with testicular histology/cytology but are not superior to FSH as predictors of the presence of sperm in testicular sperm extraction (TESE)/fine needle aspiration (FNA) biopsy in men with azoospermia.

Effects of phosphodiesterase-5 inhibitor vardenafil on testicular androgen-binding protein secretion, the maintenance of foci of advanced spermatogenesis and the sperm fertilising capacity in azoospermic men

We evaluated the effects of vardenafil on testicular androgen-binding protein secretion (ABP). Bilaterally obstructed azoospermic (OA)-men (n = 19) (group A) underwent unilateral testicular biopsy. A group of nonobstructed azoospermic (NOA)-men (n = 68) (group B) underwent bilateral testicular biopsy. ABP secretion in vitro by testicular tissue was assessed in each participant of every group. In addition, intracytoplasmic sperm injection (ICSI) cycles were performed in several couples of group A or group B using frozen/thawed spermatozoa from the biopsy material. Ten OA-men (group A1), 14 NOA-men (group B1), and nine different NOA-men (group B2) had been positive for spermatozoa in the biopsy but pregnancies were not achieved in the respective female partners. Men of groups A1, B1 and B2 were treated with vardenafil, vardenafil and L-carnitine respectively. Then, the men of groups A1, B1 and B2 underwent a second testicular (unilateral) biopsy. Within the group A1 and within the group B1, ABP secretion rate was significantly larger after vardenafil treatment than prior to vardenafil treatment. In addition, fertilisation rates in ICSI cycles within groups A1 or B1 were not affected by vardenafil administration. Vardenafil administration in NOA-men increased ABP secretion and did not affect detrimentally the presence of testicular foci of advanced spermatogenesis.

Evidence of androgen-dependent sperm storage in female reproductive tract of Scotophilus heathi

The aim of present study was to investigate the role of androgen in sperm storage in the female genital tract of Scotophilus heathi. Spermatozoa were observed in the distal part of oviduct and utero-tubal junction of all the female bats collected between January and early March. Increase in circulating testosterone level coincided with the arrangement of sperm with their head oriented towards the epithelial lining of reproductive tract. Immunocytochemical and Western blot analysis revealed the presence of androgen receptor (AR) only in the distal part of the oviduct and utero-tubal junction, the site of sperm storage. Localization of AR in the cytoplasm of luminal epithelial cells in utero-tubal junction of S. heathi suggests non-genomic action of androgen at the site of sperm storage. Further study showed the presence of intense immunoreactivity of androgen binding protein (ABP) in the glandular epithelial cells of utero-tubal junction . It is hypothesized that androgen creates a unique microenvironment e.g. secretion of ABP within lumen of utero-tubal junction which helps to store spermatozoa for prolonged period in the female genital tract of S. heathi.

Effect of Aroclor 1254 on Sertoli cellular antioxidant system, androgen binding protein and lactate in adult rat in vitro

Polychlorinated biphenyls (PCBs) are persistent and bioaccumulative environmental toxicants. Previous studies suggested that PCBs (Aroclor 1254) induce toxic effects including reproductive toxicity. The present study was designed to investigate the impact of Aroclor 1254 on Sertoli cellular function and antioxidant system of adult rat in vitro. Sertoli cells were isolated from adult rat testes and treated with various concentrations (10 −10 to 10 −7 M) of Aroclor 1254 for 6, 12 and 24 h. After the treatment period, cell viability was assessed and the Sertoli cellular antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), γ-glutamyl transpeptidase (γ-GT) and glutathione reductase (GR) and lipid peroxidation (LPO) were assayed. In addition, androgen binding protein (ABP) and lactate secretions were also quantified in Sertoli cell culture medium. Sertoli cellular viability and activity of antioxidant enzymes were significantly reduced in Aroclor 1254 (10 −10 to 10 −7 M) treatment for 6, 12 and 24 h whereas, the Sertoli cellular lipid peroxidation was significantly increased in a dose and duration dependent manner. In addition, ABP secretion diminished and lactate secretion was significantly elevated in the same manner. To conclude, the present study suggested that Aroclor 1254 disrupts Sertoli cellular metabolic functions such as ABP, lactate secretions and activity of antioxidant enzymes.

Thyroid hormones: their role in testicular steroidogenesis.

Thyroid hormones are important for growth and development of many tissues. Altered thyroid hormone status causes testicular abnormalities. For instance, juvenile hypothyroidism/neonatal transient hypothyroidism induces macroorchidism, increases testicular cell number (Sertoli, Leydig, and germ cells) and daily sperm production. Triiodothyronine (T3) receptors have been identified in sperm, developing germ cells, Sertoli, Leydig, and peritubular cells. T3 stimulates Sertoli cell lactate secretion as well as mRNA expression of inhibin-alpha, androgen receptor, IGF-I, and IGFBP-4. It also inhibits Sertoli cell mRNA expression of Müllerian inhibiting substance (MIS), aromatase, estradiol receptor, and androgen binding protein (ABP) and ABP secretion. T3 directly increases Leydig cell LH receptor numbers and mRNA levels of steroidogenic enzymes and steroidogenic acute regulatory protein. It stimulates basal and LH-induced secretion of progesterone, testosterone, and estradiol by Leydig cells. Steroidogenic factor-1 acts as a mediator for T3-induced Leydig cell steroidogenesis. Although the role of T3 on sperm, germ, and peritubular cells has not yet been completely studied, it is clear that T3 directly regulates Sertoli and Leydig cell functions. Further studies are required to elucidate the direct effect of T3 on sperm, germ, and peritubular cells.

Heregulins or Neu Differentiation Factors and the Interactions between Peritubular Myoid Cells and Sertoli Cells

Interactions between (mesenchymal) peritubular myoid cells and (epithelial) Sertoli cells play an important role in the control of Sertoli cell function and spermatogenesis. The factors involved, however, have only partially been identified. Heregulins or neu differentiation factors (NDFs) mediate mesenchymal-epithelial interactions in a variety of tissues, but their role in the testis has not been investigated. Here we demonstrate that recombinant human heregulin-α (Her-α) and Her-β stimulate transferrin and androgen-binding protein production by cultured rat Sertoli cells up to 2.5-fold. These effects are more pronounced than those of previously identified growth factors active in this assay, such as insulin-like growth factor I and basic fibroblast growth factor. Combination with these factors results in additive effects and in marked morphological changes in the Sertoli cell cultures, including formation of tubule-like structures. Stimulation of androgen-binding protein secretion is paralleled by increased levels of the corresponding messenger RNA. This parallelism was less consistent for transferrin. Semiquantitative RT-PCR indicates that the expression of NDF-α and NDF-β is more pronounced in peritubular cells than in Leydig or Sertoli cells. Conversely, the main receptors for heregulins/NDFs, HER-3 and HER-4, are predominantly expressed in Sertoli cells. A displacement assay confirms the presence of high-affinity binding sites for [125I]Her-β on intact Sertoli cells and reveals parallel displacement curves for Her-β, Her-α, and concentrated peritubular cell-conditioned medium (PTCM; estimated ED50 values: 1 ng/ml, 50 ng/ml, and 130 μg protein/ml, respectively), indicating that peritubular cells secrete one or more factors able to compete for heregulin receptors. It is concluded that heregulins/NDFs may play a role in mesenchymal-epithelial interactions in the testis. Estimates of the concentrations of heregulins in PTCM, however, make it unlikely that they contribute significantly to the effects observed with low concentrations of PTCM and ascribed to the putative mediator PModS (peritubular factor that modulates Sertoli cell function). Further investigations will be required to define the exact role of heregulins in the testis.

Heregulins or neu differentiation factors and the interactions between peritubular myoid cells and Sertoli cells.

Interactions between (mesenchymal) peritubular myoid cells and (epithelial) Sertoli cells play an important role in the control of Sertoli cell function and spermatogenesis. The factors involved, however, have only partially been identified. Heregulins or neu differentiation factors (NDFs) mediate mesenchymal-epithelial interactions in a variety of tissues, but their role in the testis has not been investigated. Here we demonstrate that recombinant human heregulin-alpha (Her-alpha) and Her-beta stimulate transferrin and androgen-binding protein production by cultured rat Sertoli cells up to 2.5-fold. These effects are more pronounced than those of previously identified growth factors active in this assay, such as insulin-like growth factor I and basic fibroblast growth factor. Combination with these factors results in additive effects and in marked morphological changes in the Sertoli cell cultures, including formation of tubule-like structures. Stimulation of androgen-binding protein secretion is paralleled by increased levels of the corresponding messenger RNA. This parallelism was less consistent for transferrin. Semiquantitative RT-PCR indicates that the expression of NDF-alpha and NDF-beta is more pronounced in peritubular cells than in Leydig or Sertoli cells. Conversely, the main receptors for heregulins/NDFs, HER-3 and HER-4, are predominantly expressed in Sertoli cells. A displacement assay confirms the presence of high-affinity binding sites for [125I]Her-beta on intact Sertoli cells and reveals parallel displacement curves for Her-beta, Her-alpha, and concentrated peritubular cell-conditioned medium (PTCM; estimated ED50 values: 1 ng/ml, 50 ng/ml, and 130 microg protein/ml, respectively), indicating that peritubular cells secrete one or more factors able to compete for heregulin receptors. It is concluded that heregulins/NDFs may play a role in mesenchymal-epithelial interactions in the testis. Estimates of the concentrations of heregulins in PTCM, however, make it unlikely that they contribute significantly to the effects observed with low concentrations of PTCM and ascribed to the putative mediator PModS (peritubular factor that modulates Sertoli cell function). Further investigations will be required to define the exact role of heregulins in the testis.

Androgen binding protein secretion and endocytosis by principal cells in the adult rat epididymis and during postnatal development.

Androgen binding protein (ABP) has been shown to be secreted by Sertoli cells and to be actively taken up by the efferent ducts and proximal caput epididymidis and, yet, to be present at high concentrations in epididymal fluids. In the present study, ABP was immunolocalized by light microscopy in epithelial cells of the efferent ducts and epididymis of adult rats and during postnatal development and by electron microscopy in specific organelles within these cells. In adults, the efferent ducts actively endocytosed Sertoli cell-derived ABP. In the epididymis, principal cells displayed a variable staining reminiscent of a checkerboardlike pattern, with cells being intensely, moderately, or weakly reactive throughout their cytoplasm or unreactive. In the electron microscope, reactive cells displayed a labeling of their Golgi apparatus and secretory vesicles indicative of an epididymal-secreted form of ABP. However, labeling was also noted over endosomes of principal cells, but only of the initial segment and intermediate zone, which, along with labeling of coated pits and vesicles, indicated that ABP was also endocytosed by principal cells of these regions. The postnatal study revealed that principal cells attained an adultlike staining pattern indicative of secretion in a region-specific manner at different ages, suggesting that ABP secretion is regulated by different factors. Ligation of the efferent ducts of 15-day-old animals revealed no reaction along the entire epididymis in animals sacrificed at later ages, suggesting the importance of luminal testicular factors in its regulation during development. In addition, as in the adult, ABP was also endocytosed by principal cells, but only in the initial segment and intermediate zone. Taken together, the present results indicate that secretion of ABP occurs along the entire epididymis, whereas endocytosis is region specific. The functional role of ABP in the epididymis in relation to sperm maturation is discussed.

Establishment of a Mouse Sertoli Cell Line Producing Rat Androgen-binding Protein (ABP)

The ultimate goal of this study was to compare the fate of rat testicular germ cells cocultured with mouse Sertoli cells that either do or do not produce rat androgen-binding protein (ABP). As a first step, we stably transfected a rat ABP expression construct into an immortalized mouse Sertoli cell line (TM4), which does not produce ABP when growing on plastic without hormones. The transfection of the pRc/CMV- rat ABP cDNA expression vector containing a neomycin resistance gene was made by either the liposome method (Dotap) or by polyethyleneimine transfection (PEI) into TM4 cell cultures. Neomycin-resistant clones were selected by adding Geneticin to the culture medium for 3 weeks. Analysis of over 25 clones revealed the presence of recombinant rat ABP when cell extracts and culture media were probed with a rabbit polyclonal antibody raised against rat testicular ABP, indicating the translation and secretion of a protein similar to rat testicular ABP. Transfected TM4 cells maintain the secretion of rat ABP for more than 40 days, with immunopositive rat ABP localized within cytoplasmic granules in the Golgi region and along cytoplasmic processes in TM4 transfected with either vector. Electron microscopic study revealed a higher development of cytoplasmic organelles involved in protein secretion.

New and traditional approaches for the assessment of testicular toxicity

In this study, the suitability of several methods for the assessment of testicular damage, including histopathology, flow cytometry (FCM), testicular sperm head counts, and secretion of androgen binding protein (ABP), has been evaluated. Testicular toxicity after acute exposure of adult rats to different doses of the known toxicant 1,3-dinitrobenzene (DNB) was analyzed. The effects showed dose dependence, in spite of the large variability within each dose group. Histopathology and FCM showed germ cell depletion, particularly of round spermatids; testicular sperm head counts were reduced and ABP production was increased. All evaluated methods showed similar sensitivities. The increased testicular ABP levels support the theory that the Sertoli cell is the likely target of DNB induced testicular toxicity, producing subsequent germ cell depletion. The presented results show the suitability of FCM for the analysis of testicular damage and also support the usefulness of including a metabolic marker for Sertoli cell function.

Reduction in fluid secretion by rat testis by drugs that block potassium channels.

The effect of two class III antiarrhythmic drugs (Almokalant, Astra-Hässle and Dofetilide, Pfizer) on fluid secretion by rat testes has been examined. Both drugs reduced fluid secretion, whether this was measured by the amount of rete testis fluid that could be collected 22 h after unilateral efferent duct ligation, or by the difference in mass between the ligated and unligated testes, or by the difference in amount of supernatant fluid after the parenchyma of the ligated and unligated testes had been dispersed and centrifuged. The secretion of potassium, calculated from the amount of potassium in the supernatant fluids from the ligated and unligated testes was also reduced by the drugs, whereas the secretion of androgen-binding protein and inositol was unaffected. The concentration of potassium in the secreted fluid, calculated from the amount and composition of the supernatant fluids, was not affected by treatment of the rats with Almokalant, but was increased in rats treated with Dofetilide and, in these, the concentration of sodium was reduced and that of magnesium and inositol was increased and the concentration of total protein was unaffected. The concentration of androgen-binding protein in secreted fluid was increased in rats treated with Almokalant, while the concentration of testosterone was unaffected. Histological examination of testes from treated rats revealed phagocytosis of stage 19 spermatids in tubules at stages VIII-IX after 2 days, at stages IX-XI after 4 days and at stages VIII-XIV after 7 days, apparently owing to an effect on spermiation. It appears that these drugs interfere with potassium-mediated fluid secretion by the testis, leading to the other changes seen.

The Effect of Cocaine and its Metabolites on Sertoli Cell Function

Purpose We determined the in vitro effects of cocaine and its 2 major metabolites, benzoylecgonine and ecgonine, on Sertoli cell function. Materials and Methods Sertoli cells were isolated from 18 to 20-day-old Sprague-Dawley rats. Sertoli cells were incubated with 4 concentrations (6.25 × 10 sup −5, 2.5 × 10 sup −4, 1 × 10 sup −3 and 4 × 10 sup −3 M./l.) of cocaine, benzoylecgonine and ecgonine for 24, 48 and 72 hours. Transferrin and androgen-binding protein secretion was measured to determine the effect of cocaine and its metabolites on Sertoli cell function. Results Cocaine, benzoylecgonine and ecgonine had the ability to decrease transferrin secretion. The 2 highest doses of cocaine (1 × 10 sup −3 and 4 × 10 sup −3 M./l.) significantly decreased transferrin production at 24, 48 and 72 hours. The effects of benzoylecgonine and ecgonine on transferrin production were less pronounced than those of cocaine. Androgen-binding protein secretion was also decreased by exposure to cocaine and its metabolites although the decrease was less marked compared to that of transferrin production. Conclusions We demonstrated in vitro harmful effects of cocaine and its 2 major metabolites on Sertoli cell function, as measured by transferrin and androgen-binding protein production.

The effects of a gonadotropin-releasing hormone antagonist on androgen-binding protein distribution and other parameters in the adult male rat.

The effects of gonadotropins and gonadal steroids on androgen-binding protein (ABP) production and its distribution among the epididymis, seminiferous tubule fluid (STF), testicular interstitial fluid (TIF), and blood were studied in 300-g adult male Sprague-Dawley rats. The rats either received no treatment or their pituitary function was suppressed by administration of the GnRH antagonist [AcD2Nal,D4ClDPhe2,D3Pal3,Arg5,DGlu6 (AA),D-Ala10]LHRH (antagonist). Other groups of rats were treated with hCG, FSH, FSH plus hCG, testosterone, or estradiol, alone or together with antagonist. Treatment was conducted for 30 days, after which time, ABP was detected by its ability to bind [3H]5 alpha-dihydrotestosterone. Transport of ABP from the testis to the epididymis was inhibited by antagonist administration. Simultaneous treatment with antagonist and hCG, or antagonist and hCG plus FSH prevented antagonist-induced inhibition of ABP transport. Neither FSH, testosterone, nor estradiol alone was effective in this process. Inhibition of ABP transport to the epididymis was accompanied by its accumulation within the testis. Treatment with antagonist and FSH resulted in a 4.5-fold increase in the concentration of ABP in TIF, but had little effect on the amount of ABP in STF, indicating selective secretion of ABP from the basal surface of the Sertoli cells. Treatment with antagonist alone, antagonist together with testosterone or estradiol, or estradiol alone resulted in increased concentrations of ABP in both TIF and STF, but the increase in TIF was proportionately greater. Treatment with hCG or FSH plus hCG alone or with antagonist not only facilitated ABP transport to the epididymis, but also increased TIF levels of ABP above control values. The former treatment resulted in increased concentrations of testosterone in TIF, but not in STF. Both treatments resulted in testosterone levels in both compartments that were higher than those in animals treated with antagonist alone. No treatment had a statistically significant effect on blood levels of ABP. About 50% of ABP synthesis appears to be constitutive, i.e. is not regulated by hormones. Although ABP production continues in the presence of antagonist, its transport to the epididymis is halted, indicating that epididymal transport of ABP is a hormone-dependent process. It is likely that elevated intratesticular levels of testosterone or FSH and testosterone acting in concert regulate epididymal transport of ABP.

Effects of Smoking on Testicular Function, Semen Quality and Sperm Fertilizing Capacity

Purpose The effects of smoking on testicular function and sperm physiology were studied. Materials and Methods Left testicular biopsy was performed in 49 smokers and 28 nonsmokers. Seminal specimens from these men were analyzed. Results Testosterone levels in the left testicular vein, left testicular androgen-binding protein secretion rate (in vitro), sperm motility, percentage of morphologically normal spermatozoa, sperm morphometric parameters and outcome of sperm function tests were significantly lower (p less than 0.05) in smokers than in nonsmokers. Conclusions Morphological sperm abnormalities due to secretory dysfunction of the Leydig and Sertoli cells may be the cause of impaired sperm fertilizing capacity in smokers.

Secreted products and extracellular matrix from testicular peritubular myoid cells influence androgen-binding protein secretion by Sertoli cells in culture.

Metabolic cooperation mediated by secreted factors between Sertoli cells and peritubular myoid cells has been well documented. We have confirmed that factors secreted by peritubular myoid cells modulate androgen-binding protein (ABP) secretion by Sertoli cells and shown further that this can also be achieved with peritubular myoid cell extracellular matrix (ECM). While peritubular myoid cell ECM potentiated the stimulatory effect of dibutyryl cyclic AMP on Sertoli cell ABP secretion, secreted factors did not, suggesting that the two components influence Sertoli cells through distinct mechanisms. We also tested other factors and other cell lines for effects on ABP production by Sertoli cells. The addition of human plasma fibronectin or conditioned medium from the basement membrane-producing Englebreth-Holm-Swarm sarcoma also stimulated ABP secretion by Sertoli cells. Cocultures of epithelial Sertoli cells with the cells of mesenchymal origin, such as testicular peritubular myoid cells, embryonic skin fibroblasts, and bladder smooth muscle cells, significantly stimulated ABP secretion by Sertoli cells, but coculture with the epithelial-derived Martin-Darby canine kidney cell line had no effect on Sertoli cell-secreted ABP levels. Our data further define the epithelial-mesenchymal cell interaction that exists between Sertoli cells and peritubular myoid cells in the mammalian testis.

Steroidogenic and morphogenic characteristics of human peritubular cells in culture.

We have explored the morphogenic and functional characteristics of human peritubular cells originating from seminiferous tubule (ST) fragments isolated from the testes of two prepubertal patients with the androgen insensitivity syndrome. These ST were cultured in Dulbecco's Modified Eagle's Medium-Ham's F-12 supplemented with antibiotics, transferrin, hydrocortisone, vitamin E, and 3% fetal bovine serum. A centrifugal growth of elongated fibroblast-like cells peripheral to the ST explants was observed. Muscle-specific actin and 3 beta-hydroxysteroid dehydrogenase were evident in the peritubular area and in the elongated cells growing from the tubules. Histochemistry was negative in the tubules themselves, revealing the mixed nature of these cultures. The ST fragments were lost after subculturing, leaving a homogeneous monolayer of fibroblast-like cells. The steroidogenic potential of these cells was demonstrated by the secretion of testosterone (T) to the culture medium. T secretion was stimulated by hCG in a time-dependent fashion (patient 1: Day 11, 84% and Day 15, 200%; patient 2: Day 8, 73% and Day 11, 32% over basal). FSH also stimulated T secretion (patient 1: Day 5, 136% and Day 8, 89%; patient 2: Day 8, 117% and Day 11, 129% over basal). Furthermore, T secretion by these cultures was 100% higher than that observed in mesenchymal cells obtained from the testicular intertubular space in the same patient. Spontaneous T secretion and hormone responses declined progressively to cease by 25 days in culture. These results suggested the involvement of Sertoli cell (SC)-secreted factor(s) in the regulation of T secretion by peritubular cells. In order to further explore possible paracrine interactions between peritubular and Sertoli cells, we carried out heterologous cocultures with rat SC. After 72 h a striking redistribution of both cell types was observed with the formation of cord-like structures. Ultrastructural examination of these cords showed the formation of a basement membrane between epithelial (Sertoli) and mesenchymal cells of peritubular origin. No resumption of T secretion was observed, but an increase in androgen-binding protein (ABP) production by rat SC under basal (37%) and FSH-stimulated (52%) conditions was evident. Our results show that in the human peritubular compartment, cells exist that can alternatively express steroidogenic functions, associate with SC in a specific mesenchymal-epithelial interaction, and exert regulatory influences on ABP secretion by SC. In addition they indicate that communicating events in the testis are preserved throughout evolution.

Bilateral effect of unilateral vasectomy on testicular testosterone biosynthesis

Tweive immature male dogs underwent a left vasectomy (group A). An additional five underwent a sham operation (group B). Sixteen weeks after the surgery, the bilateral mean values for caudal epididymal sperm content, the percentage of motile spermatozoa, intratesticular testosterone concentration, and testicular secretion of androgen-binding protein (in vitro) were significantly lower in group A. The mean peripheral serum testosterone responses 3 hours after human chorionic gonadotropin stimulation (3,000 IU) were significantly lower in group A than in group B (6.3 ng/mL v 9.5 ng/mL). These findings indicate a bilateral deficiency in both Leydig and Sertoli cell secretory function in unilaterally vasectomized dogs, resulting in impaired bilateral spermatogenesis and sperm maturation. The authors suggest that unilateral injuries of the vas deferens during hernia operations in children may result in bilateral testicular dysfunction.

Is infancy a quiescent period of testicular development? Histological, morphometric, and functional study of the seminiferous tubules of the cebus monkey from birth to the end of puberty.

The objective of this study was to describe the maturational changes observed in the seminiferous tubules of the monkey Cebus apella, a New World primate species, from birth to the end of puberty. Nineteen animals were subdivided into four groups: neonatal (1-40 days), infantile (4 months to 1 yr), early pubertal (1 yr, 8 months to 2 yr, 9 months), and late pubertal (4-8 yr). Volumetric determinations of different testicular components were made, tubule diameter and length were calculated, and spermatogenic cells, Sertoli cells, and androgen-binding protein secretion were quantified. Testicular and seminiferous tubule volumes increased significantly in the first 5 months of life and during puberty due to the combined increment in seminiferous tubule diameter and length. The total number of spermatogonia increased until late puberty to stabilize subsequently. Spermatocytes and spermatids appeared during puberty and increased dramatically until the end of this period. The germ cell ratios, indicative of spermatogenic efficiency, improved continuously in late puberty coincidentally with a reduction of spermatocyte degeneration. Sertoli cells proliferated in the neonatal and infantile periods, determining a longitudinal growth of the seminiferous tubules, but remained stable during puberty, when androgen-binding protein secretion increased significantly. The multiplication of germ cells is the main factor responsible for the increment in tubule diameter during puberty and determines the most noticeable postnatal modification of testicular volume. During late puberty, the reduction of spermatocyte degeneration leads to an increment in germ cell ratios and a progressive, but slow, improvement of spermatogenic efficiency, explaining why pubertal development of the testis occurs over such a prolonged period in this primate. This is in contrast to what happens in most laboratory animals and suggests that the Cebus is a useful model for studies of human male puberty.

Human sertoli cells in vitro: Morphological features and androgen-binding protein secretion

Sertoli cells play a pivotal role in the regulation of spermatogenesis as they provide the anatomical basis of the blood-testis barrier. In the present paper we report some results of our studies on the ultrastructural features, the responsiveness to FSH, and the ability to secrete androgen-binding protein (ABP) of human Sertoli cells in vitro. The nucleus showed the characteristic foldings of the nuclear membrane, scattered chromatin, and a fibrillar nucleolus. In the cytoplasm Charcot-Boettcher crystals were present and active phagocytic activity was documented by the presence of vacuoles containing lipids and cellular debris. Human Sertoli cells in culture responded to FSH with a maximal rise in cAMP that was approx. 3-fold. This response to FSH is comparable to that reported for the adult rat but lower than that of the immature rat, and suggests that human as well as rat Sertoli cells could have a reduced response to FSH since sexual maturation was achieved. As no evidence has been reported on ABP secretion by human Sertoli cells in culture we evaluated the concentration of this protein in the Sertoli cell spent media. Human Sertoli cells in culture produced ABP and the response to FSH was dose-related. The K d value of human ABP (hABP) was approx. 7.5 nM, being slightly higher than that of the rat ABP and an order of magnitude different from that of sex hormone-binding globulin (SHBG) present in human plasma. We also measured the association and dissociation rates of dihydrotestosterone-hABP complexes and the K d K a ratio was very close to the value of K d of the Scatchard analysis. The differences between hABP and SHBG may open the way to the selective measurement of ABP in many conditions of male infertility.