Androgen binding protein as a marker for Sertoli cell function

Leydig Cell and Spermatogenesis

Leydig cells of the testis have the capacity to synthesize androgen (mainly testosterone) from cholesterol. Adult Leydig cells are the cell type for the synthesis of testosterone, which is critical for spermatogenesis. At least four steroidogenic enzymes take part in testosterone synthesis: cytochrome P450 cholesterol side chain cleavage enzyme, 3β-hydroxysteroid dehydrogenase, cytochrome P450 17α-hydroxylase/17,20-lyase and 17β-hydroxysteroid dehydrogenase isoform 3. Testosterone metabolic enzyme steroid 5α-reductase 1 and 3α-hydroxysteroid dehydrogenase are expressed in some precursor Leydig cells. Androgen is transported by androgen-binding protein to Sertoli cells, where it binds to androgen receptor to regulate spermatogenesis.

50 years of spermatogenesis: Sertoli cells and their interactions with germ cells

The complex morphology of the Sertoli cells and their interactions with germ cells has been a focus of investigators since they were first described by Enrico Sertoli. In the past 50 years, information on Sertoli cells has transcended morphology alone to become increasingly more focused on molecular questions. The goal of investigators has been to understand the role of the Sertoli cells in spermatogenesis and to apply that information to problems relating to male fertility. Sertoli cells are unique in that they are a nondividing cell population that is active for the reproductive lifetime of the animal and cyclically change morphology and gene expression. The numerous and distinctive junctional complexes and membrane specializations made by Sertoli cells provide a scaffold and environment for germ cell development. The increased focus of investigators on the molecular components and putative functions of testicular cells has resulted primarily from procedures that isolate specific cell types from the testicular milieu. Products of Sertoli cells that influence germ cell development and vice versa have been characterized from cultured cells and from the application of transgenic technologies. Germ cell transplantation has shown that the Sertoli cells respond to cues from germ cells with regard to developmental timing and has furthered a focus on spermatogenic stem cells and the stem cell niche. Very basic and universal features of spermatogenesis such as the cycle of the seminiferous epithelium and the spermatogenic wave are initiated by Sertoli cells and maintained by Sertoli-germ cell cooperation.

Trends of SHBG and ABP levels in male farmers: Influences of environmental fluoride exposure and ESR alpha gene polymorphisms

A number of epidemiological studies have reported that chronic exposure to high concentrations of fluoride not only causes dental and skeletal fluorosis but additionally affects serum levels of reproductive hormones. However, possible interaction between fluoride exposure and estrogen receptor alpha (ESRα) gene polymorphisms on sex hormone-binding globulin (SHBG) and androgen binding protein (ABP) of male farmers has not been detailed. Here, we conducted a cross-sectional study including 348 male farmers with different fluoride exposure levels from drinking water in Henan province of China to explore effects of fluoride exposure and ESRα genetic variation on serum SHBG and ABP levels. We found serum SHBG levels in male farmers from the high exposure group to be lower than those of the low exposure group. We also found that concentrations of SHBG affected ABP levels. Furthermore, fluoride exposure and single nucleotide polymorphisms at the XbaI and rs3798577 loci of the ESRα gene affected serum ABP levels. Our findings suggest that chronic fluoride exposure from drinking water is associated with alterations of serum SHBG and ABP concentrations in local male farmers and that the effect of fluoride exposure on ABP levels vary depending on ESRα gene polymorphisms.

Reduced testosterone and Ddx3y expression caused by long-term exposure to arsenic and its effect on spermatogenesis in mice

Arsenic (As) has been recognized as a cause of male reproductive toxicity. However, effects of long-term arsenic exposure (puberty-adult) on spermatogenesis, testosterone synthesis, and the expression of androgen binding protein (ABP) and Ddx3y remain unclear. The objective of this investigation was to explore these effects and the underlying mechanisms. Male mice were treated with 5 and 50 ppm arsenic for 6 months via drinking water. The results showed that arsenic reduced sperm count and sperm motility and enhanced the abnormal sperm percentage. The decrease in the number of spermatogenic cells and sperm in seminiferous tubules and the decline in the Johnsen score were observed in both arsenic-treated groups, suggesting spermatogenesis disorders. Moreover, arsenic diminished serum testosterone, along with the reduced expression of luteinizing hormone receptor (LHR), steroidogenic acute regulatory protein (StAR) and 17-β-hydroxysteroid dehydrogenase (17β-HSD) genes. Arsenic also down-regulated mRNA levels of ABP and Ddx3y in a dose-dependent manner. Meanwhile, the protein levels of StAR, 17β-HSD and Ddx3y were significantly reduced in arsenic-treated groups. Taken together, these results suggest that the reduced testosterone through inhibition of the expression of multiple genes responsible for the biosynthesis, the damaged androgen homeostasis partially via lessening the expression levels of the ABP gene and the down-regulated expression of Ddx3y, may contribute to spermatogenesis disorders in mice exposed to arsenic.

In utero exposure to di-(2-ethylhexyl) phthalate induces testicular effects in neonatal rats that are antagonized by genistein cotreatment

Fetal exposure to endocrine disruptors (EDs) is believed to predispose males to reproductive abnormalities. Although males are exposed to combinations of chemicals, few studies have evaluated the effects of ED mixtures at environmentally relevant doses. Our previous work showed that fetal exposure to a mixture of the phytoestrogen genistein (GEN) and the plasticizer di-(2-ethylhexyl) phthalate (DEHP) induced unique alterations in adult testis. In this follow-up study, we examined Postnatal Day 3 (PND3) and PND6 male offspring exposed from Gestational Day 14 to parturition to corn oil, 10mg/kg GEN, DEHP, or their combination, to gain insight into the early molecular events driving long-term alterations. DEHP stimulated the mRNA and protein expression of the steroidogenic enzyme HSD3B, uniquely at PND3. DEHP also increased the mRNA expression of Nestin, a Leydig progenitor/Sertoli cell marker, and markers of Sertoli cell (Wt1), gonocyte (Plzf, Foxo1), and proliferation (Pcna) at PND3, while these genes were unchanged by the mixture. Redox (Nqo1, Sod2, Sod3, Trx, Gst, Cat) and xenobiotic transporter (Abcb1b, Abcg2) gene expression was also increased by DEHP at PND3, while attenuated when combined with GEN, suggesting the involvement of cellular stress in short-term DEHP effects and a protective effect of GEN. The direct effects of GEN and mono-(2-ethylhexyl) phthalate, the principal bioactive metabolite of DEHP, on testis were investigated in PND3 organ cultures, showing a stimulatory effect of 10 μM mono-(2-ethylhexyl) phthalate on basal testosterone production that was normalized by GEN. These effects contrasted with previous reports of androgen suppression and decreased gene expression in perinatal rat testis by high DEHP doses, implying that neonatal effects are not predictive of adult effects. We propose that GEN, through an antioxidant action, normalizes reactive oxygen species-induced neonatal effects of DEHP. The notion that these EDs do not follow classical dose-response effects and involve different mechanisms of toxicity from perinatal ages to adulthood highlights the importance of assessing impacts across a range of doses and ages.

The battle of the sexes for stroke therapy: female- versus male-derived stem cells

Cell therapy is a major discipline of regenerative medicine that has been continually growing over the last two decades. The aging of the population necessitates discovery of therapeutic innovations to combat debilitating disorders, such as stroke. Menstrual blood and Sertoli cells are two gender-specific sources of viable transplantable cells for stroke therapy. The use of autologous cells for the subacute phase of stroke offers practical clinical application. Menstrual blood cells are readily available, display proliferative capacity, pluripotency and angiogenic features, and, following transplantation in stroke models, have the ability to migrate to the infarct site, regulate the inflammatory response, secrete neurotrophic factors, and have the possibility to differentiate into neural lineage. Similarly, the testis-derived Sertoli cells secrete many growth and trophic factors, are highly immunosuppressive, and exert neuroprotective effects in animal models of neurological disorders. We highlight the practicality of experimental and clinical application of menstrual blood cells and Sertoli cells to treat stroke, from cell isolation and cryopreservation to administration.

Influence of persistent thyroxine reduction on spermatogenesis in rats neonatally exposed to 2,2',4,4',5,5'-hexa-chlorobiphenyl

BACKGROUND

The aim of the present study is to determine the long-term testicular effects of neonatal exposure to PCB153.

METHODS

Sprague-Dawley (SD) rats were treated by oral gavage with PCB153 in corn oil at doses of 0, 0.025, and 2.5 mg/kg per day from postnatal day 3 (PND 3) to PND7. The rats were sacrificed on PND 8 and PND 77. TUNEL in situ detection for testis apoptosis, immunohistochemical staining of thyroid gland for thyroxine (T4), semi-quantitative RT-PCR for mRNA expression, and radioimmunoassay (RIA) for serum hormone levels were performed.

RESULTS

Neonatal treatment with PCB153 at both doses had no obvious effects on body weight, testis weight, testis histology, and germ cell apoptosis, but decreased T4 staining in thyroid gland was observed on PND 8. On PND 77, neonatal treatment with 2.5 mg/kg per day of PCB153 significantly reduced daily sperm product (DSP). Serum levels of thyroxine (T4) and free thyroxine (FT4) decreased, but there were no differences in thyroid-stimulating hormone (TSH) level between the control and exposed groups. Gap junction connexin43 (CX43) and cyclin-dependent kinase inhibitor (CDKI) P27kip1 mRNA expression, which was associated with Sertoli cell differentiation, was significantly reduced after PCB153 treatment on PND 8 but not on PND 77. Androgen-binding protein (ABP) and androgen receptor (AR) mRNA expression, which indicates Sertoli cell maturation, was suppressed on PND 77 after neonatal PCB153 exposure.

CONCLUSIONS

The findings in this study suggest that neonatal exposure to PCB153 induces persistent T4 reduction, which disturbs Sertoli cell function, and subsequently results in alterations in adult spermatogenesis. Birth Defects Res (Part B) 89:18-25, 2010. (c) 2009 Wiley-Liss, Inc.

Adjudin-mediated germ cell depletion alters the anti-oxidant status of adult rat testis

Successful spermatogenesis is dependent on the proper attachment of developing germ cells to Sertoli cells. Manipulation of these interactions by drugs like Adjudin can hamper the development of germ cells and lead to conditions of temporary infertility. Although studies have shown the contraceptive potential of Adjudin, much is not known about its action in the testis. In this study, we sought to investigate the effect of Adjudin on the oxidative status of mammalian testis. Adult male rats were administered with a single dose of Adjudin (50 mg/kg body weight) by oral gavage and were killed at 1, 2, 4, 7, 15, or 30 days of treatment. Adjudin caused a significant increase in the production of hydrogen peroxide and lipid peroxidation from 4 to 7 days after treatment. There was a significant decrease in the activities of anti-oxidant enzymes superoxide dismutase, catalase, glutathione peroxidase and glutathione S-transferase from 4 to 7 days after treatment with Adjudin. However, the state of oxidative stress was less pronounced from 15 to 30 days after Adjudin treatment. The level of androgen binding protein (ABP) remained unchanged following Adjudin treatment. These results show that there is an induction of oxidative stress accompanying adherens junction restructuring which suggests a role for reactive oxygen species in the regulation of these testicular junctions. However, transient elevation in reactive oxygen species levels did not affect androgen transport.

Role of basic helix-loop-helix (bHLH) and CREB transcription factors in the regulation of Sertoli cell androgen-binding protein expression

Differentiation of Sertoli cells is marked by the presence of novel gene products such as transferrin and androgen-binding protein (ABP). Transcriptional regulation of Sertoli cell differentiation is, in part, controlled through the binding of specific transcription factors to response elements within these genes promoters. Transferrin gene expression has been shown to be regulated by the binding and interactions of basic helix-loop-helix (bHLH) and cAMP response element binding protein (CREB) to an E-box and cyclic AMP response element (CRE), respectively. Interaction between the bHLH and CREB is facilitated through subsequent binding of CREB-binding protein (CBP)/p300. The hypothesis tested in the current study is that ABP expression is regulated by a similar mechanism. The ABP promoter activation was analyzed through the use of transfection assays, site-directed mutagenesis, and electromobility shift assays (EMSA). Transient transfections of rat Sertoli cells used a reporter construct containing the proximal 619 bp of the ABP promoter. Observations suggest that cAMP and follicle stimulating hormone (FSH) upregulate the expression of ABP. Mutational studies of the three E-boxes and the CRE of the 619-bp ABP promoter indicate that all of these elements are critical for stimulation of promoter activity. EMSA revealed a weak interaction between an E-box-2 and the CRE that are overlapping in the promoter. An artificial promoter that contains only an E-box and CRE was created to further test this hypothesis. The artificial promoter was stimulated by both FSH and cAMP. Experiments with mutants of the artificial promoter demonstrate that both response elements contribute to the optimal activation of the promoter construct. The overexpression of the bHLH inhibitor Id (i.e., inhibitor of differentiation) that binds bHLH proteins and eliminates DNA binding was found to suppress hormone activation of the ABP promoter. Combined observations of the ABP promoter and artificial promoter provide insight into a common mechanism for gene regulation in differentiated Sertoli cells involving a role for both the bHLH and CREB family of transcription factors.

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), gamma-glutamyl transpeptidase (gamma-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.

Co-expression of vasopressin and androgen-binding protein in the rat hypothalamus

In previous studies we have observed the expression of androgen binding protein (ABP) in the rat hypothalamo-neurohypophysial system. With immunocytochemical double staining we found partial co-localization with oxytocin. In the present study we used antibodies to the anti-diuretic hormone arginine vasopressin (AVP) for co-localization with ABP in the rat hypothalamus. Both antigens were seen in the magnocellular paraventricular and supraoptic nuclei. Dense fiber networks with varicosities containing both AVP and ABP immunoreactivity were visible throughout the hypothalamus, the median eminence and in the posterior pituitary lobe. Double immunostaining revealed also co-existence in the parvocellular portion of the paraventricular nucleus and in the suprachiasmatic nucleus. ABP immunoreactive neurons in the preoptic region were devoid of AVP staining, AVP neurons in the bed nucleus of the stria terminalis stained only occasionally for ABP. We conclude that both the magnocellular and the parvocellular hypothalamic vasopressin systems are capable of expressing the steroid binding globulin, which is probably subject to axonal transport, along with the peptide hormone. Intrahypothalamic expression of ABP may be among the mechanisms necessary for rapid actions of steroids on hypothalamic neuroendocrine systems.

Distribution of androgen-binding protein in the rat hypothalamo-neurohypophyseal system, co-localization with oxytocin

Androgen-binding protein (ABP) is known to be expressed in the male and female rat hypothalamus. In the present study, we observed immunocytochemically ABP in neurons of the magnocellular hypothalamic nuclei, in the preoptic region and in the lateral hypothalamus. Dense fiber networks with varicosities, containing ABP immunofluorescence, were visible throughout the hypothalamus, the median eminence and in the posterior pituitary lobe. Double immunostaining revealed a partial coexistence of ABP-and oxytocin immunoreactivity in a portion of the magnocellular perikarya. ABP was isolated by affinity chromatography from hypothalamus homogenates. Western blots resulted in immunoreactive (IR) bands with an approximate molecular weight of 35 and 50 kDa. Mass spectrometry of these preparations confirmed the presence of ABP, which was almost identical to ABP isolated from rat testis. It is likely that ABP, expressed in magnocellular oxytocinergic neurons, is subject to axonal transport and release in the hypothalamo-neurohypophyseal system.

Dynamics of testicular germ cell apoptosis in normal mice and transgenic mice overexpressing rat androgen-binding protein

The number and type of testicular germ cells undergoing apoptosis in different age groups of mice (from 7 to 360 days of age) was determined and compared in age-matched wild type (WT) control and in a transgenic (TG) mice homozygous to rat androgen binding protein (ABP) using flow cytometry. Flow cytometric quantification revealed that the total number of germ cells undergoing apoptosis did not differ significantly in WT and TG mice up to Day 14. From Day 21 to Day 60, the number of germ cells undergoing apoptosis was consistently higher in TG than in WT mice. Starting from Day 90, the number of germ cells undergoing apoptosis in TG mice was lower than controls until Day 360. In 21-60 days old TG mice, spermatogonia, S-Phase cells, and primary spermatocytes are the cell types undergoing apoptosis at significantly greater numbers than those in WT mice. However, starting from day 60, the total number of spermatids undergoing apoptosis was significantly lower in TG mice than in age-matched WT controls. TdT-mediated dUTP-biotin nick end labeling (TUNEL) in testicular sections from TG mice of 21 and 30 days of age confirmed the presence of increased numbers of apoptotic germ cells compared to their age matched controls. These data indicate that the continuous presence of greater than physiological concentrations of ABP in the mouse testis has a biphasic effect on the frequency of apoptosis in germ cells. The initial pre-pubertal increase in testicular germ cell apoptosis may result from direct or indirect actions of ABP and is likely to determine the subsequent life-death balance of germ cell populations in TG mice, whereas the subsequent reduction may result from maturation depletion. A wave of apoptosis during the pre-pubertal period is required for normal spermatogenesis to develop, and our data indicate that this apoptotic wave may be regulated by ABP and/or androgens.

Dynamics of testicular germ cell proliferation in normal mice and transgenic mice overexpressing rat androgen-binding protein: a flow cytometric evaluation

Transgenic mice carrying rat androgen-binding protein (ABP) genomic DNA express high amounts of testicular ABP and develop a progressive impairment of spermatogenesis. To understand the mechanism of these changes, we have studied the pattern of testicular germ cell proliferation from 7 to 360 days of age in wild-type (WT) control and transgenic homozygous (ABP-TG) mice by flow cytometry after labeling DNA in isolated germ cells with propidium iodide. At all ages studied, the body weight of the ABP-TG mice was lower than that of age-matched WT controls. Significantly reduced testicular weight and total germ cell number in the ABP-TG mice were evident from Day 30 and Day 60, respectively. Flow cytometric analysis of isolated germ cells revealed that the number of germ cells undergoing proliferation (S-phase cells) was identical in WT control and ABP-TG mice up to Day 14. Subsequently, the number of germ cells in S-phase was consistently higher in ABP-TG than in WT mice. The number of primary spermatocytes was significantly increased starting from Day 60, and the numbers of round and elongated spermatids were significantly reduced in the ABP-TG animals from Day 21 and Day 60 onwards, respectively. Immunocytometry for intracellular ABP at 90 days of age revealed that the percentage of ABP-containing germ cells was greater in ABP-TG than in WT mice. The continuous presence of ABP in mouse seminiferous tubules at greater than physiological concentrations facilitates the formation of primary spermatocytes but impairs subsequent transformation to round and elongated spermatids. Based on our observations and the analysis of the available literature, the most likely mechanism for production of these effects is sustained reduction in the bioavailability of androgens.

Effect of surgically induced varicocele on testicular blood flow and Sertoli cell function

OBJECTIVES

To evaluate the effect of varicocele on testicular blood flow and expression by Sertoli cells of transferrin and androgen-binding protein (ABP), to determine whether varicoceles impair Sertoli cell function.

METHODS

Experimental varicocele was established in male Sprague-Dawley rats by partial ligation of the left renal vein. The control group received a sham operation. At 30 minutes after surgery, rats underwent a xenon-133 washout study, and at 30 days after surgery, transferrin, ABP, and testicular blood flow were evaluated. Expression of transferrin and ABP were evaluated using immunohistochemical techniques. Testicular blood flow was measured using xenon-133 clearance techniques. Statistical analyses were done with an independent t test.

RESULTS

The testicular blood flow was 16.7 +/- 1.25 mL/100 g/min in varicocele-bearing rats and 21.01 +/- 0.46 mL/100 g/min in sham-operated rats 30 minutes after surgery. Testicular blood flow remained decreased at 30 days in varicocele-bearing rats (15.12 +/- 1.08 mL/100 g/min) and remained stable in the control group (19.45 +/- 0.55 mL/100 g/min). The expression of transferrin and ABP was significantly reduced in varicocele-bearing rats compared with the control group.

CONCLUSIONS

Our study suggests that a decrease in testicular blood flow may lead to impaired Sertoli cell function in varicocele-bearing rats.

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.

Distribution of immunoreactive androgen-binding protein/sex hormone-binding globulin in tissues of the fetal rat

Androgen-binding protein/sex hormone-binding globulin (ABP/SHBG) is an extracellular carrier protein that binds androgens and estrogens with high affinity. In the adult, ABP/SHBG is thought to function in the male reproductive system and the general circulation in both sexes to modulate the actions of sex steroids. The ABP/SHBG gene is also expressed in the embryonic rat liver, where SHBG is secreted into the fetal blood of male and female rats. The embryo also expresses an alternative SHBG with a unique N-terminal sequence. In this study, the distribution of immunoreactive SHBG in the 17-day-old male fetal rat was determined with six antisera. In general, all of the antisera reacted with the same structures. Specific tissue immunoreactivity was mostly cytoplasmic and/or extracellular. By far the most prominent immunoreactive structures were the mesoderm-derived tissues: connective tissue, striated and cardiac muscle, cartilage, and the liver hematopoietic system. In addition, all regions of the fetal brain contained immunoreactive neurons. In the developing male reproductive system, there was minor reactivity in the testicular cords, whereas the connective tissue in the differentiating Wolffian duct stained with all of the antisera. The Wolffian duct epithelium and epithelia in other developing organs contained small amounts of immunoreactive SHBG, except for the lung, which stained in the epithelial extracellular matrix. An antibody raised against a unique N-terminal peptide specific for the alternative SHBG protein revealed that it was also present in many tissues. These data suggest that SHBG is important for the differentiation of mesodermal tissues. SHBG may modulate the action of androgens in embryonic stroma, thereby regulating development of the epithelium in hormone-dependent tissues.

Structure, function, and regulation of androgen-binding protein/sex hormone-binding globulin

Despite over 20 years of research, the functions of ABP and SHBG remain elusive. The major reason for this lack of knowledge has been the unavailability of natural mutants with clinical defects for study. There is strong evidence that these binding proteins do act to modulate the gene regulatory actions of nuclear sex steroid receptors by controlling the availability of androgens and estrogens. In plasma, SHBG controls the metabolic clearance rate of sex steroids. In addition there is strong evidence that they have a much broader function. The identification of plasma membrane receptors in target tissues and the finding of homologous domains in several developmental proteins support other functions. Moreover, other experiments suggest the proteins may actually be hormones or growth factors. These findings are not compatible with a model that has the proteins only regulating free steroid hormone levels. Obviously, much more experimentation will be necessary to reveal the functions of ABP and SHBG. The recent discoveries have offered several clues to their functions and open new routes for study. These experiments, coupled with newly developed techniques, such as gene knockout by homologous recombination, make one optimistic that the functions of these unique proteins will be deciphered in the near future.

Soy of dietary source plays a preventive role against the pathogenesis of prostatitis in rats

This study examined the effects of diet on the development of prostatitis in male rats. Adult male rats were placed on either of two specially formulated diets which differed from one another by the presence or absence of soy as the protein source. A third group of rats (control) was fed standard laboratory rat chow which also includes soy as a source of protein. After 11 weeks, it was found that rats maintained on soy-free diet developed prostatitis mainly in the lateral lobe of the prostate. Increased severity and incidence of prostatitis in rats maintained on the soy-free diet coincided with a significant decrease in urinary excretion of various phytoestrogens. There was no evidence of prostatitis in rats maintained on soy-containing diets. Urinary excretion of phytoestrogens in rats maintained on soy-containing diet was also not different from controls. These results suggest that soy as a dietary source plays a protective role against the development of prostatitis in rats, and indicate that the ventral, lateral and dorsal lobes of the rat prostate have different sensitivities to alterations in dietary factors.

Lead acetate does not impair secretion of Sertoli cell function marker proteins in the adult Sprague Dawley rat

This study was conducted to determine the effects of lead on Sertoli cell function. Androgen binding protein and inhibin in testicular fluids and classical parameters of the hypothalamic-pituitary-gonadal axis were measured in adult male rats. For 10 wk, the rats were given water that contained 0.05%, 0.1%, 0.5%, and 1% lead acetate. Serum follicle-stimulating hormone, luteinizing hormone, and testosterone levels in all animals that ingested lead were normal at the middle and end of the experiment, as was the pituitary content of follicle-stimulating hormone and luteinizing hormone. Histologic examination revealed no disruption of spermatogenesis. Distribution of androgen binding protein in serum, seminiferous tubular fluid, and interstitial fluid was normal, as was the concentration of inhibin in interstitial fluid and seminiferous tubular fluid. However, a significant increase in epididymal androgen binding protein level and a decrease in seminal vesicle weight were observed in rats that ingested water containing 1% lead acetate. These results suggest that the effect of lead on spermatogenesis is not marked in adult Sprague Dawley rats, nor does Sertoli cell function appear to be affected adversely. Lead has been reported to alter in vitro metabolic function of Sertoli cells obtained from 16- to 21-d-old Sprague Dawley rats, and the Sertoli cells of juvenile animals may be more susceptible to lead than those of adult animals. The significant decrease in seminal vesicle weight and the abnormal epididymal androgen binding protein content indicate that lead could affect the male reproductive function in Sprague Dawley rats via its action on male accessory organs.

Exploration of the testis in infertile men. Relationships among serum levels of FSH, LH, 17-alpha-OH-progesterone and testosterone

A considerable body of evidence is available indicating a paracrine relationship between the seminiferous tubules and the Leydig cells. In 113 adult subjects in basal conditions the blood levels were determined of FSH (follicle stimulating hormone), LH (luteinizing hormone), 17-alpha-OH-P (17-alpha-OH-progesterone) and T (testosterone) either as a whole or as a free fraction. According to the sperm counts and the FSH levels, the studied subjects were divided into three groups: a group N (Normozoospermia) with sperm counts greater than 20 million/ml and FSH levels of 2.5 +/- 1.5 (mean +/- SD, mIU/ml), a group MO (moderate oligozoospermia) with mild degree of oligozoospermia (5-10 mill) and FSH levels in the range found in group N, a group SO (severe oligozoospermia) with severe degree of oligozoospermia (sperm count less than 5 mill/ml) and FSH levels greater than 2 SD the mean value in the N. Serum levels of LH, 17-alpha-OHP, total T, free T and FSH/LH, LH/T, 17-alpha-OHP/T ratios in group MO and SO were compared with those found in the group N.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged suppression of rat testis function by a depot formulation of Zoladex, a GnRH agonist

A sustained-release formulation of a potent gonadotropin-releasing hormone (GnRH) agonist, Zoladex (D-Ser(But),6 Aza Gly10-GnRH; ICI 118,630; goserelin), was administered subcutaneously (3.6 mg/depot) to male rats once every 28 days for 2-24 wk to determine the extent to which pituitary-testis function could be suppressed and whether suppression was maintained throughout the period of treatment. Administration of Zoladex resulted in sustained decreases in weight of the testis, epididymis, seminal vesicles and prostate gland. The decreases were apparent within 2 wk of initiating treatment. Patchy degeneration of the seminiferous tubules and atrophy of the Leydig cells were observed, but did not progress beyond the degree observed after 1 month of treatment. Serum and testis testosterone were markedly depressed after 2 wk of treatment, as was testis [125I]hCG binding. Serum gonadotropins were also reduced by treatment. Serum androgen binding protein (ABP) was elevated, testis ABP content remained unchanged, and epididymal ABP content was reduced. The changes are consistent with the hypothesis that this compound affects both the anterior pituitary gland and the testis. These findings indicate that depot delivery systems are a convenient way to administer GnRH analogs for sustained treatment schedules.

Serum and testicular testosterone and androgen binding protein profiles following subchronic treatment with carbendazim

While the general toxicity of the benzimidazole pesticides for mammals is low, one of these compounds, carbendazim (MBC), causes degeneration of testicular tissue and decreases spermatogenic activity at doses well below the LD50 value. A study conducted by S. D. Carter, R. A. Hess, and J. W. Laskey (1987, Biol. Reprod. 37, 709-717) showed that treatment with 400 mg/kg/day MBC resulted in severe seminiferous tubular atrophy and infertility. Since spermatogenesis is an androgen-dependent process, we characterized the effects of MBC (0-400 mg/kg/day) on the endocrine function of the rat testes. Following subchronic (85 day) exposure, serum hormones (TSH, LH, FSH, and Prl) were measured as were androgen binding protein (ABP) and testosterone in testicular fluids (interstitial fluid and seminiferous tubule fluid). In addition, the functional capacity of the Leydig cell to secrete testosterone was assessed in vitro following an hCG challenge. Subchronic treatment with MBC at doses of 50-100 mg/kg/day had no effect on pituitary or testicular hormone concentrations: 200 mg/kg/day elevated the testosterone concentration in the seminiferous tubule fluid and the ABP concentration in both the interstitial fluid and the seminiferous tubule fluid without affecting serum testosterone or ABP concentrations. The 400 mg/kg/day dose resulted in increased concentration of both testosterone and ABP in the interstitial fluid and seminiferous tubule fluid and elevated serum ABP, with no change in serum testosterone. This endocrine profile is consistent with the testicular atrophy and "Sertoli cell-only" syndrome seen in these animals as reported by Gray et al. (1987, Toxicologist 7, 717). We conclude that seminiferous tubule fluid testosterone may be a result of two factors: (1) increased interstitial fluid testosterone concentrations and (2) decreased testosterone outflow from the testis to the general circulation. Also, increased ABP in the interstitial fluid may reflect a change in the relative secretion of ABP into the interstitial fluid and the seminiferous tubules.

Zinc acetate pretreatment ameliorates cisplatin-induced Sertoli cell dysfunction in Sprague-Dawley rats

The present study was undertaken to determine if prior administration of zinc acetate (ZnAc) or copper sulfate (CuSO4) could prevent pituitary, Leydig, or Sertoli cell dysfunction subsequent to cisplatin administration in adult Sprague-Dawley rats. Animals were given cisplatin at a dose of 2 mg/kg daily for 5 days, with or without the i.p. administration of ZnAc (6 mg/kg per day) or CuSO4 (5 mg/kg per day), beginning 5 days prior to and continuing through the administration of cisplatin. Control animals were given vehicle, ZnAc1, or CuSO4. Animals were sacrificed 1 week after the initial cisplatin injection. Cisplatin administration resulted in suppressed serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels as well as a 77% reduction in serum testosterone and an 82% reduction in testicular testosterone. The concomitant administration of either ZnAc or CuSO4 did not result in a significant difference relative to animals receiving cisplatin alone, although administration of both cations alone significantly reduced testicular testosterone content. Serum androgen-binding protein (ABP) was not significantly lowered in any treatment group. There was a marked reduction of 57% in testicular ABP content relative to control values subsequent to cisplatin administration. This reduction was partially prevented by ZnAc treatment: the testicular ABP concentration was only 15% lower than that in controls (not significant). Since the cisplatin-induced reduction in serum FSH was not altered by ZnAc pretreatment, we conclude that the near normalization of testicular ABP content may be evidence of improved Sertoli cell function. In contrast, cisplatin-induced decreases in the serum gonadotropins and testicular androgens were not lessened by pretreatment with either cation. Further studies may be warranted to determine whether ZnAc pretreatment has a beneficial effect on spermatogenesis during cisplatin treatment.

Effects of the benomyl metabolite, carbendazim, on the hypothalamic-pituitary reproductive axis in the male rat

Carbendazim (MBC), the bioactive metabolite of the fungicide benomyl, has been reported to induce a number of testicular alterations in male rats. Since it is possible that extragonadal changes contribute to the appearance of such effects, the present study focused on the presence of concurrent endocrine changes in the hypothalamic and pituitary components of the brain-pituitary-testicular axis. Subchronic administration of MBC (50, 100, 200 or 400 mg/kg) was found to cause a dose-related elevation in serum follicle stimulating hormone (FSH) and pituitary luteinizing hormone (LH). Values for prolactin and thyroid-stimulating hormone remained unchanged. No statistical differences in gonadotropin-releasing hormone concentrations were present in mediobasal hypothalamus, although an elevation in anterior hypothalamic values was found at the low dose, followed by a dose-related decline. These findings demonstrate that previously reported gonadal differences following subchronic exposure to carbendazim are accompanied by alterations elsewhere in the reproductive system which appear to involve both changes in Sertoli cell-pituitary feedback signals and direct effects of the compound on the central nervous system.

Characterization of cis-platinum-induced Sertoli cell dysfunction in rodents

The present study examined the effects of dosage and frequency of cis-platinum administration on various aspects of Sertoli cell function and its correlation with the status of spermatogenesis in rats 1 and 9 weeks after the initial drug administration. Adult male Sprague-Dawley rats were administered cis-platinum (10 mg/kg) intraperitoneally as a single dose or as five daily doses of 2 mg/kg. Electron microscopic observation of testicular tissues fixed in the presence of lanthanum revealed that cis-platinum administration resulted in leakage of the Sertoli cell tight junctions. This occurred as early as 24 hr after the five daily injections, and persisted at least 40 days. Testicular androgen-binding protein (ABP) content was not significantly affected by either treatment regimen after 1 or 9 weeks of recovery. On the other hand, serum ABP values were significantly elevated after 9 weeks of recovery. In addition, the increased sodium and decreased potassium concentrations in seminiferous tubular fluid noted in cis-platinum-treated animals were also indicative of abnormal Sertoli cell secretory function. Degeneration of spermatogenic cells was noted as early as 5 days after the last drug administration; and partial restoration of spermatogenesis was noted after 40 days of recovery. We conclude that in rats both morphological and biochemical properties of Sertoli cells are affected by cis-platinum administration. These changes in Sertoli cell function may be responsible for the cis-platinum-induced impairment of spermatogenesis in these animals.

Physiology of the male reproductive system: endocrine, paracrine and autocrine regulation

This presentation reviews the male reproductive system, concentrating on newer advances in our knowledge of its physiology, biochemistry, and regulation, and introduces the topic of male reproductive toxicology. GnRH is the hypothalamic peptide responsible for the stimulation of LH and FSH release from the pituitary. It is synthesized as a pro-hormone, processed in the hypothalamus and released into the portal system in a pulsatile fashion. The timing of these pulses is critical to the release of LH and FSH into the general circulation. While LH and FSH are the main trophic hormones for the testis, we now realize the importance of not only endocrine control, but also of paracrine and autocrine regulation. Specifically, the local control of Leydig cells, Sertoli cells, and germ cells appears to be modulated by numerous growth factors and local regulators arising from within the testis. This point is emphasized both during a discussion of the interaction of the various cell types in the testis and during a discussion of spermatogenesis, where techniques which show stage-specific secretions are highlighted. Newest advances in the mechanism of action of steroidal and peptide hormones are also emphasized with special reference to the possible interaction between toxicants and endocrine control of the reproductive system. This update of the reproductive system "sets the stage" for an in-depth examination of the site and mechanism of action of reproductive toxicants.

Changes in testicular and serum hormone concentrations in the male rat following treatment with m-dinitrobenzene

m-Dinitrobenzene (m-DNB)-induced testicular atrophy has been attributed to a direct effect upon the germinal epithelium. However, such degenerative changes in the germinal epithelium should induce shifts in the testicular hormonal milieu, which would in turn alter the hypothalamic-pituitary gonadal axis in general. This study evaluated the endocrine status of male rats (killed 3 hr, 24 hr, 1 week, and 2 weeks) following a single oral dose of m-DNB (32 mg m-DNB/kg). Serum and pituitary leuteinizing hormone, follicle-stimulating hormone (FSH), and protactin and hypothalamic gonadotropin-releasing hormone (GnRH) concentrations were determined. Testosterone and androgen-binding protein concentrations in serum, interstitial fluid, seminiferous tubule fluid, and caput epididymis were also determined. In vitro basal and hCG-stimulated testosterone release was determined in the decapsulated testis. Results of the present study indicate that pituitary hormone concentrations and hypothalamic GnRH were unaffected after a single oral dose of m-DNB. Serum FSH was elevated at 2 weeks. There was a transient decrease in serum testosterone at 24 hr, which returned to control values at 1 and 2 weeks. Interstitial fluid, seminiferous tubule fluid, and caput epididymal testosterone concentrations were increased at 1 and 2 weeks. Basal testosterone release in vitro was increased at 2 weeks, while hCG-stimulated testosterone release was increased at 1 and 2 weeks. Androgen-binding protein concentrations in serum and interstitial fluid were increased at 1 and 2 weeks. Androgen-binding protein was increased at 24 hr and 1 week in seminiferous tubule fluid, but returned to control concentrations by 2 weeks. However, the total tubular content of androgen-binding protein was dramatically decreased at 2 weeks. Androgen-binding protein in the caput epididymis was unaltered following m-DNB treatment. These data demonstrate that m-DNB exerts a direct effect on the testes and not through alterations in hypothalamic and pituitary control of gonadal function.

Androgen binding protein in serum, testis and epididymis following treatment with the Leydig cell cytotoxic agent, ethylene dimethanesulphonate

Androgen binding protein (ABP) was measured in the serum, testes and epididymides of adult male rats after treatment with ethylene dimethanesulphonate (EDS), which has direct cytotoxic effects on Leydig cells and secondarily affects sperm production. Serum ABP increased to a maximum 7 days after treatment and remained elevated for most of the 63 days of observation. The ABP content of both the epididymides and testes declined and were low between 14 days and 21 days following treatment. By contrast, the concentration of ABP in these tissues was maintained after EDS treatment and was sometimes elevated. This divergence between ABP content and concentration was due to atrophy of the testes and epididymides after the decline in androgen secretion. The changes in serum and tissue ABP levels after EDS occurred earlier than those observed in adult hypophysectomized animals, possibly due to local paracrine influences that are lost secondarily to destruction of the Leydig cells. Testicular testosterone did not parallel ABP content as it fell dramatically 2 days after EDS and remained low for about 21 days before returning to near control values after 63 days. Testicular and epididymal sperm heads decreased in number after EDS, but were not clearly associated with the changes in ABP. The results confirm that androgens are important for the production of ABP and for the partitioning of this protein between the blood and the lumen of the reproductive tract.

Protein secretions of Sertoli cells

As was stated in the introduction, many of the functions of the Sertoli cells are apparently carried out by the protein secretions of these cells. The use of Sertoli cell cultures and appropriate biochemical and immunological techniques has allowed the characterization of some of these secretion products. It is likely that many of the functions of the Sertoli cells are necessary because of the presence of the blood-testis barrier. Many growth and nutritive factors which are necessary for cell viability are available to most cells via the serum. The germinal cells within the adluminal compartment do not have access to serum factors and one of the functions of the Sertoli cells is to synthesize serum-like components and secrete them into the adluminal compartment. The historical description of Sertoli cells as "nurse cells" thus appears to have been accurate. The nurse-cell function is most clearly demonstrated by the proposed mechanism by which germinal cells obtain ferric ions. The Sertoli cells have developed a system to move serum-derived iron through their own cytoplasm and to secrete it bound to newly synthesized testicular transferrin molecules which can deliver it to specific receptors on the germinal cell surface (Huggenvik et al., 1984). Functionally, all of the secreted proteins from Sertoli cells which have been characterized or proposed fall into one of five basic classes. First, Sertoli cells secrete a number of transport proteins including transferrin, ceruloplasmin, and ABP. The proposed function of these proteins is the transport of Fe3+, Cu2+, and androgens to the germinal cells or to the epididymis (ABP). Second, Sertoli cells synthesize and secrete a number of proteins which have a hormone-like or growth factor-like activity. AMH is a clear and well-documented example of this type of product while the evidence for inhibin, somatomedin C, EGF-like growth factor, and seminiferous growth factor will require further corroboration. Third, Sertoli cells secrete proteins which have enzymatic activities. Plasminogen activator is the best characterized example of this class of products and the alpha-lactalbumin-like activity is of potential interest. The fourth class of Sertoli cell secretion products includes those proteins which contribute to the basement membrane, namely, type IV collagen and laminin. Finally, there is a very important group of Sertoli cell secretion products for which there is, as yet, no evidence for a defined function. This group includes SGP-1 and SGP-2 which are the major sertoli cell products in rats and which have been well-characterized biochemically.(ABSTRACT TRUNCATED AT 400 WORDS)

Changes in the secretion of ABP into testicular interstitial fluid with age and in situations of impaired spermatogenesis

Androgen-binding protein (ABP) was measured in serum and testicular interstitial fluid (IF) from rats during sexual maturation or in adult rats in which impairment of spermatogenesis had been induced by (i) testosterone withdrawal following Leydig cell destruction, (ii) local heating (43 degrees C) of the testes for 30 min or (iii) induction of unilateral cryptorchidism (UCD). The changes observed were related to the IF levels of testosterone and, in most instances, to the serum levels of FSH. The levels of ABP in serum and IF decreased together with age, being highest at 30 days, falling steeply by 40 days and then slowly but progressively up to 100 days of age. A similar pattern was observed for serum FSH, except that the initial fall occurred beyond 40 days of age. Treatment with EDS or exposure to local heating caused comparable reductions in testicular weight (25-30% by 7 days after treatment, 50% by 21-28 days) and raised the serum levels of FSH. In both groups the levels of ABP in IF were increased by two- to three-fold while the levels of testosterone were either reduced markedly (EDS-treatment) or remained unchanged (local heating). In rats made UCD for 60 days, the weight of the abdominal testis was reduced by 75%, compared with the contralateral scrotal testis, while the IF levels of ABP and testosterone were significantly increased (55%) and decreased (90%), respectively. Short-term (3 days) deprivation of testosterone in adult rats, following immunoneutralization of LH, was without significant effect on IF levels of ABP. It is concluded that ABP secretion into IF is increased in situations of subnormal (or sub-adult) numbers of germ cells and this is usually associated with high levels of FSH. Measurement of ABP levels in IF should prove of value for the monitoring of Sertoli cell function in vivo and may be of diagnostic use for the detection of changes in germ cell numbers.

Effects of ethane dimethane sulphonate (EDS) on seminiferous tubule function in rats

The effects of a single injection of ethane dimethane sulphonate (EDS) on aspects of seminiferous tubule function were assessed over a period of 49 days. Ethane dimethane sulphonate, which is known to cause destruction of Leydig cells, reduced the levels of testosterone in both serum and testicular interstitial fluid for 21 days, after which recovery occurred. The low testosterone levels were associated with elevated serum levels of LH and FSH. Daily sperm production was decreased from 14 to 42 days post-EDS but returned to control levels at 49 days. The production of seminiferous tubule fluid, measured after unilateral efferent duct ligation, decreased significantly at 7 and 14 days but then recovered. The testicular content of androgen binding protein (ABP) was decreased from 14 to 28 days but returned to normal thereafter. These results demonstrate significant effects on seminiferous tubule function, which may be due to the decrease in testosterone or be associated with a direct effect of EDS.

Peritubular cells influence Sertoli cells at the level of translation

Conditioned medium from cultured peritubular cells (PTCM) was capable of increasing the incorporation of amino acids into acid-precipitable material in cultured Sertoli cells, while the incorporation of uridine into acid-precipitable material was unaffected. PTCM did not influence intracellular cAMP accumulation in a manner similar to follicle-stimulating hormone (FSH). PTCM was able to stimulate androgen-binding protein (ABP) secretion by Sertoli cells even in the presence of a maximal dose of FSH. PTCM increased the rate at which peptides are elongated 5-fold over control medium or medium from control fibroblasts. These studies indicate that peritubular cells influence Sertoli cells through different mechanisms than FSH and exert their influence, at least in part, at the level of translation by increasing the rate of peptide elongation.

Seminiferous epithelial function in the pubertal rat following local testicular irradiation

The dose- and time-related responses of the irradiated seminiferous epithelium in the pubertal rat have been investigated. The threshold dose for Sertoli cell dysfunction, as assessed by serum androgen binding protein (ABP) concentrations, was estimated to be 5 Gy. A significant reduction (to less than 50% of control levels) in serum ABP was observed at 8 weeks post-irradiation, with further reductions at later times (24 and 36 weeks). Serum follicle-stimulating hormone (FSH) was elevated to between 130 and 175% of control at only 2 weeks post-irradiation, but recovered with time. Normal FSH levels seemed to be related to recovery of spermatogenesis, as assessed by counts of regenerating tubule cross-sections. The results indicate that the clonogenic spermatogonia and Sertoli cells of the pubertal rat testis are less sensitive to radiation than those of the adult.

Concentrations of free testosterone, total testosterone, and androgen binding protein in the peripheral serum of male rats during sexual maturation

To investigate the relationship between free testosterone and sexual maturation in the male rat, animals were decapitated every 5 days from 25 through 75 days of life. Serum was assayed for androgen binding protein and total testosterone by radioimmunoassay. Free testosterone concentrations were calculated from the total testosterone concentration and the free testosterone fraction. The free testosterone fraction was determined by ultrafiltration. The pubertal increase in relative prostate and relative seminal vesicle weights began between 45 and 50 days and 40 and 45 days, respectively. Although the over-all trend in the free testosterone fraction was to increase with increasing age (r = 0.46, P less than 0.0001), there was a significant secondary peak at 50 days. The serum concentration of androgen binding protein was highest on day 25, fell rapidly until day 40, and declined slowly thereafter. Despite these variations in both androgen binding protein and the free testosterone fraction during sexual maturation, the calculated serum concentration of free testosterone was remarkably similar in pattern to that of total testosterone (r = 0.99, P less than 0.0001). These data indicate that the serum concentration of total testosterone is an accurate reflection of the serum concentration of free testosterone during the sexual maturation of the male rat.

Extracellular matrix regulates Sertoli cell differentiation, testicular cord formation, and germ cell development in vitro

Sertoli cell preparations isolated from 10-day-old rats were cultured on three different substrates: plastic, a matrix deposited by co-culture of Sertoli and peritubular myoid cells, and a reconstituted basement membrane gel from the EHS tumor. When grown on plastic, Sertoli cells formed a squamous monolayer that did not retain contaminating germ cells. Grown on the matrix deposited by Sertoli-myoid cell co-cultures, Sertoli cells were more cuboidal and supported some germ cells but did not allow them to differentiate. After 3 wk however, the Sertoli cells flattened to resemble those grown on plastic. In contrast, the Sertoli cells grown on top of the reconstituted basement membrane formed polarized monolayers virtually identical to Sertoli cells in vivo. They were columnar with an elaborate cytoskeleton. In addition, they had characteristic basally located tight junctions and maintained germ cells for at least 5 wk in the basal aspect of the monolayer. However, germ cells did not differentiate. Total protein, androgen binding protein, transferrin, and type I collagen secretion were markedly greater when Sertoli cells were grown on the extracellular matrices than when they were grown on plastic. When Sertoli cells were cultured within rather than on top of reconstituted basement membrane gels they reorganized into cords. After one week, tight junctional complexes formed between adjacent Sertoli cells, functionally compartmentalizing the cords into central (adluminal) and peripheral (basal) compartments. Germ cells within the cords continued to differentiate. Thus, Sertoli cells cultured on top of extracellular matrix components assume a phenotype and morphology more characteristic of the in vivo, differentiated cells. Growing Sertoli cells within reconstituted basement membrane gels induces a morphogenesis of the cells into cords, which closely resemble the organ from which the cells were dissociated and which provide an environment permissive for germ cell differentiation.

The effects of the indazole carboxylic acid derivative, tolnidamine, on testicular function: I. Early changes in androgen binding protein secretion in the rat

The indazole carboxylic acid derivative, tolnidamine, has marked antispermatogenic activity in several animal species. In this study, we assessed the effect of tolnidamine on rat Sertoli cell function both in vivo and in vitro, using androgen binding protein (rABP) as a marker. Groups of six male rats were killed 2, 4, 8, 16, 32, 64 hours and 5, 8, and 12 days following tolnidamine administration (250 mg/kg by oral gavage). There was a progressive reduction in both testicular and epididymal weights. Serum FSH levels did not change and LH showed a transient increase between 64 hours and 8 days. Except for an initial increase at 2 hours, there were no changes in serum testosterone. Epididymal rABP concentration and content declined as early as 8 hours, with the lowest values occurring at 5 and 12 days. By 16 hours, there was an increase in testicular rABP, which was also evident at 8 days and 12 days. Within 16 hours after tolnidamine, there was a rise in serum rABP, which persisted until the end of the experiment. When another indazole carboxylic acid derivative, lonidamine, was administered (250 mg/kg), similar changes were evident in epididymal and serum rABP at 32 hours, but the rapid decrease in testicular rABP suggested a different mechanism of action. In another experiment, single oral doses of tolnidamine (50, 100, 250, and 500 mg/kg) were administered to other groups of rats and the animals were killed after 24 hours and 5 days. With increasing doses of tolnidamine, there was a reduction in epididymal rABP concomitant with an increase in testis and serum rABP levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental pattern of androgen-binding protein secretion during the critical period of sexual differentiation

Androgen-binding protein (ABP) distribution in the fluids and tissues of fetal and neonatal rats was determined by radioimmunoassay during the critical period of sexual differentiation from 12 days postconception (PC) to 6 days postpartum. No significant differences in plasma ABP concentrations were detected between litters of the same age. Fetal plasma ABP in both sexes was high at 18 days PC and decreased to birth. At birth, this level increased, then continued its decline during the neonatal period. After 4 days, the level in females was significantly lower than that of males; this was the only time a significant difference in ABP levels between the sexes was observed. Amniotic fluid ABP was low at 12 days and increased to a peak at 18 days PC. Thereafter, it decreased as in plasma. ABP concentrations in fetal livers and placentas were almost negligible and changed in parallel with fluid concentrations. No ABP was detected in maternal plasma. Fetal production of ABP begins at the approximate time of gonadal differentiation and reaches a peak at 18 days, the time of peak androgen production. ABP may function as a protection against excessive concentrations of free androgen in the developing fetus and neonate.

The hormonal regulation of premeiotic steps of spermatogenesis in the newborn rat

.he effect of high doses of testosterone propionate (TP) on the development of the first spermatogenic wave was systematically analyzed to determine the period of maximal susceptibility to testosterone. Two mg of TP were administered daily to groups of immature male rats, starting from birth, or days 5, 10, 15, and 20 until day 35 of life. Animals injected from birth or day 5 showed severe testicular atrophy, with reductions of more than 70% of testicular weight, diminished tubular diameters, and spermatogenic arrest during the meiotic prophase. Groups treated from days 10 or 15 showed increasing testicular weights with qualitatively normal spermatogenesis. When treatment started at 20 days, completely normal testicular development was achieved. To test the responsiveness of the neonatal hypothalamo-pituitary axis to TP administration, groups of 5-day-old male rats received daily injections of TP, and plasma FSH was determined at ten, 20, and 35 days. FSH levels were not detectable at ten and 20 days, and extremely depressed at 35. A group of 5-day-old male rats was injected simultaneously with 2 mg of TP and 14 IU of FSH (human menopausal gonadotropin: 71 IU of FSH and 80 IU of LH/ml) until day 35. Testicular weights and tubular diameters were increased compared to controls, and spermatid differentiation had proceeded to more mature steps than those seen in control animals. Inhibition of testicular development by neonatal TP administration was paralleled by a sharp decrease in circulating FSH levels and reversed by FSH replacement.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of streptozotocin-induced hyperglycaemia on androgen-binding protein in rat testis and epididymis

In adult male rats treated with streptozotocin 6 weeks before the experiments, androgen-binding protein concentration was increased in testicular tissue by 33% (p less than 0.01) and reduced in epididymal tissue by 25% (p less than 0.005) in animals exhibiting severe hyperglycaemia as compared with animals remaining in normoglycaemia or moderate hyperglycaemia. Androgen-binding protein content was diminished in epididymal tissue by 40% (p less than 0.0005) but not changed in testicular tissue. If related to constant body weight, the sum of testicular and epididymal androgen-binding protein was identical in both normo- and hyperglycaemic animals. This disturbance in androgen-binding protein distribution may be the consequence of altered testicular secretion or impaired transport of androgen-binding protein from testes to epididymides.

Dynamics of SHBG response to testosterone. Implications upon the immediate biological effect of sex hormones

The dynamics of the changes in serum concentrations of SHBG to variations in serum testosterone was studied in rabbits. Castration of male rabbits failed to produce changes in SHBG within 2 days but induced a significant increment 2 months later. Administration of 15 mg of testosterone to 5 male castrates produced a rapid decrease in SHBG concentrations from 215 +/- 121 nmol/l before, to 114 +/- 15, 6 h after (mean +/- SD), while 25 mg of the androgen barely changed SHBG levels in 5 females (from 81 +/- 26 to 72 +/- 22). Three of the males and the 5 females showed a tendency to recover basal levels at 24 and 48 h. Since SHBG is a major regulator of the availability of sex hormones to be transported into tissue cells for both biological action and degradation, the rapid changes in serum SHBG induced by testosterone might play a role in controlling its own biological effect. A decrease in SHBG will result in a more effective stimulation in androgen-responsive tissues, but it will also favor a faster interruption of the effect by increasing the rate of degradation. These androgen induced changes in SHBG are apparently different in male and females.