Androgen Binding Research Articles

Paxillin Regulates Androgen- and Epidermal Growth Factor-induced MAPK Signaling and Cell Proliferation in Prostate Cancer Cells

Although transcriptional effects of androgens have been extensively studied, mechanisms regulating transcription-independent (nongenomic) androgen actions are poorly understood. Previously, we have shown that paxillin, a multidomain adaptor protein, is a critical regulator of testosterone-induced MAPK-signaling during Xenopus oocyte maturation. Here we examine the nongenomic effects of dihydrotestosterone (DHT) in prostate cancer cells, focusing on how paxillin mediates Erk signaling and downstream physiologic actions. We show that in LnCAP cells DHT functions as a growth factor that indirectly activates the EGF-receptor (EGFR) via androgen receptor binding and matrix metalloproteinase-mediated release of EGFR ligands. Interestingly, siRNA-mediated knockdown of paxillin expression in androgen-dependent LnCAP cells as well as in androgen-independent PC3 cells abrogates DHT- and/or EGF-induced Erk signaling. Furthermore, EGFR-induced Erk activation requires Src-mediated phosphorylation of paxillin on tyrosines 31/118. In contrast, paxillin is not required for PKC-induced Erk signaling. However, Erk-mediated phosphorylation of paxillin on serines 83/126/130 is still needed for both EGFR and PKC-mediated cellular proliferation. Thus, paxillin serves as a specific upstream regulator of Erk in response to receptor-tyrosine kinase signaling but as a general regulator of downstream Erk actions regardless of agonist. Importantly, Erk-mediated serine phosphorylation of paxillin is also required for DHT-induced prostate-specific antigen mRNA expression in LnCAP cells as well as EGF-induced cyclin D1 mRNA expression in PC3 cells, suggesting that paxillin may regulate prostate cancer proliferation by serving as a liaison between extra-nuclear kinase signaling and intra-nuclear transcriptional signals. Thus, paxillin may prove to be a novel diagnostic or therapeutic target in prostate cancer.

Isolation and structure elucidation of a novel androgen antagonist, arabilin, produced by Streptomyces sp. MK756-CF1

In the course of screening for a new type of androgen receptor (AR) antagonist, we isolated a novel compound, arabilin, with two structural isomers, spectinabilin and SNF4435C, produced by Streptomyces sp. MK756-CF1. Structure elucidation on the basis of the spectroscopic properties showed that arabilin is a novel polypropionate-derived metabolite with a p-nitrophenyl group and a substituted γ-pyrone ring. Arabilin competitively blocked the binding of androgen to the ligand-binding domain of AR in vitro. In addition, arabilin inhibited androgen-induced prostate-specific antigen mRNA expression in prostate cancer LNCaP cells.

Cadmium suppresses the proliferation of piglet Sertoli cells and causes their DNA damage, cell apoptosis and aberrant ultrastructure

ObjectiveVery little information is known about the toxic effects of cadmium on somatic cells in mammalian testis. The objective of this study is to explore the toxicity of cadmium on piglet Sertoli cells.MethodsSertoli cells were isolated from piglet testes using a two-step enzyme digestion and followed by differential plating. Piglet Sertoli cells were identified by oil red O staining and Fas ligand (FasL) expression as assayed by immunocytochemistry and expression of transferrin and androgen binding protein by RT-PCR. Sertoli cells were cultured in DMEM/F12 supplemented with 10% fetal calf serum in the absence or presence of various concentrations of cadmium chloride, or treatment with p38 MAPK inhibitor SB202190 and with cadmium chloride exposure. Apoptotic cells in seminiferous tubules of piglets were also performed using TUNEL assay in vivo.ResultsCadmium chloride inhibited the proliferation of Piglet Sertoli cells as shown by MTT assay, and it increased malondialdehyde (MDA) but reduced superoxide dismutase (SOD) and Glutathione peroxidase (GSH-Px) activity. Inhibitor SB202190 alleviated the proliferation inhibition of cadmium on piglet Sertoli cells. Comet assay revealed that cadmium chloride caused DNA damage of Piglet Sertoli cells and resulted in cell apoptosis as assayed by flow cytometry. The in vivo study confirmed that cadmium induced cell apoptosis in seminiferous tubules of piglets. Transmission electronic microscopy showed abnormal and apoptotic ultrastructure in Piglet Sertoli cells treated with cadmium chloride compared to the control.Conclusioncadmium has obvious adverse effects on the proliferation of piglet Sertoli cells and causes their DNA damage, cell apoptosis, and aberrant morphology. This study thus offers novel insights into the toxicology of cadmium on male reproduction.

Oxidative Stress and NAD+ in Ischemic Brain Injury: Current Advances and Future Perspectives

Numerous studies have indicated oxidative stress as a key pathological factor in ischemic brain injury. One of the key links between oxidative stress and cell death is excessive activation of poly(ADP-ribose) polymerase-1 (PARP-1), which plays an important role in the ischemic brain damage in male animals. Multiple studies have also suggested that NAD+ depletion mediates PARP-1 cytotoxicity, and NAD+ administration can decrease ischemic brain injury. A number of recent studies have provided novel information regarding the mechanisms underlying the roles of oxidative stress and NAD+-dependent enzymes in ischemic brain injury. Of particular interest, there have been exciting progresses regarding the mechanisms underlying the roles of NADPH oxidase and PARP-1 in cerebral ischemia. For examples, it has been suggested that androgen signaling and binding of PARP-1 onto estrogen receptors could account for the intriguing findings that PARP-1 plays remarkably differential roles in the ischemic brain damage of male and female animals; and some studies have suggested casein kinase 2, copper-zinc superoxide dismutase, and estrogen signaling can modulate the expression and activity of NADPH oxidase. This review summarizes these important current advances, and proposes future perspectives for the studies on the roles of oxidative stress and NAD+ in cerebral ischemia. It is increasingly likely that future studies on NAD- and NADP-dependent enzymes, such as NADPH oxidase, PARP-1, and sirtuins, would expose novel mechanisms underlying the roles of oxidative stress in cerebral ischemia, and suggest new therapeutic strategies for treating the debilitating disease.

Analysis of androgen-and progestin receptors in human endometrial carcinomas.

Androgen-binding components labeled with a tritiated synthetic androgen, methyltrienolone(R1881) were analysed in human endometrial carcinoma cytosols. Tritiated R1881 binding consists of 3 components; high-affinity, low capacity androgen binding (androgen receptor), possible progestin receptor and non-specific androgen binding. The existence of androgen receptor in the tumor suggests a direct effect of androgen in endometrial carcinoma, possibly, through its interaction with the androgen receptor. Androgen- and progestin receptors were further measured in the cytosols of 20 endometrial carcinomas from 19 non-treated patients. The concentrations of the androgen receptors in the endometrial carcinomas were, in decreasing order; highly differentiated [21.5 + 5.4(SEM) fmoles/mg protein, N=10], moderately differentiated [3.4 + 2.7, N=3] and poorly differentiated tumors [2.5 + 1.4, N=7]. The concentrations of progestin receptors in the highly differentiated, moderately differentiated and poorly differentiated tumors were 291 + 79.7 (N=10), 52.6 + 34.1(3) and 14.7 + 6.8(7), respectively. Androgen- and progestin receptors in endometrial carcinomas would appear to correlate with histologic grade of differentiation of the tumor.

Effects of PFNA exposure on expression of junction-associated molecules and secretory function in rat Sertoli cells

Perfluorononanoic acid (PFNA, C9), a synthetic perfluorinated chemical containing nine carbons, has been identified in humans and wildlife worldwide. Sertoli cell plays a key role in spermatogenesis; however, the toxic effects of PFNA on Sertoli cells have not been studied. The aim of this study was to investigate the effects of PFNA exposure on cell junction molecules and factors specifically secreted by Sertoli cells. Primary Sertoli cells from 20- to 21-day-old rats were exposed to increasing PFNA concentrations (0, 1, 10, 25, 50, or 75 μM) for 24 h. No significant changes in the expression of cytoskeleton-associated molecules were noted, although the mRNA levels of vimentin were upregulated dramatically in cells exposed to 50 and 75 μM PFNA. Meanwhile, the mRNA levels of Sertoli cell-specific secretions, such as Mullerian inhibiting substance (MIS), androgen binding protein (ABP), inhibin B, transferrin, and follicle-stimulating hormone receptor (FSH-R) changed significantly in experimental groups. Wilms’ tumor gene (WT1), a transcription factor, was upregulated significantly in cells exposed to 1–75 μM PFNA. In additional studies, male rats were exposed to 0, 1, 3, or 5 mg/kg-d PFNA for 14 days. Vacuoles in the cytoplasm of Sertoli cells were observed in the ultrastructure of testis. Furthermore, the changes in the concentrations of MIS and inhibin B in serum and the protein levels of WT1 and transferrin in testis were similar to the mRNA expression levels of those observed after in vitro treatment. In conclusion, these findings demonstrated that PFNA treatment led to the damage of specific secretory functions of Sertoli cells and that these effects might be an underlying cause of the male-specific reproductive toxicity of PFNA.

Is the “Comb Over” Dying? A Mouse Model for Male Pattern Baldness (Androgenic Alopecia)

Androgenic alopecia (AGA) is also known as male pattern baldness, but it affects males and females. In males, AGA results in the commonly observed loss of hair from the top of the head but not on the sides. In women, the result is a general thinning of hair. At least 50% of men will have AGA by their 50th birthday and up to 70% of males will have AGA in later life. It is estimated that 6% of women under age 50 are affected and 30–40% of women aged 70 and over have AGA (1). Hair growth initiates at the base of the hair follicle in the hair bulb (Fig. 1). Cell proliferation occurs in the matrix of the hair bulb, after which the keratinocytes move up into the follicle, differentiating into the layers of the hair and its surrounding sheaths. The process occurs in a repeating cycle initiated with a growth phase (anagen) of 2–7 yr in humans followed by regression (catagen, 2 wk), and a quiescent phase (telogen, 3 months) during which hairs are shed until reentry into anagen to generate a new hair shaft in the existing follicle (2, 3). For individuals with AGA, there is progressive shortening of anagen, resulting in increased shedding of the short-lived hairs, while the follicles produce shorter, finer hairs. The dermal papilla composed of specialized fibroblasts located below the hair bulb is thought to supply the inductive signals needed to control the growth and differentiation of the hair shaft (4, 5). Paradoxically, androgens are major contributors of hair loss for the scalp but stimulate hair growth in other areas. Men castrated before puberty do not develop AGA, but AGA can be triggered in castrated men after injection of testosterone (6). The levels of androgen receptor (AR) are elevated in balding scalp (7, 8) and individuals who lack AR (androgen insensitivity syndrome) do not display AGA (9). The enzyme 5 -reductase that converts testosterone to the more potent dihydrotestosterone (DHT) is also elevated in the balding scalp, and AGA is not observed in men with a congenital deficiency of 5 -reductase (8). Elevated 5 -reductase levels are thought to be the major cause of AGA. In fact, the 5 -reductase inhibitor finasteride can be used to treat AGA, but the use of finasteride is contraindicated in pregnant women because it can cause malformation of the external genitalia of male fetuses (10). The mechanisms by which androgens and AR regulate hair growth have not been fully established. However, it is accepted that androgens can act by at least two pathways to alter cellular physiology. In the classical pathway, androgen binding to the intracellular AR results in a conformational change in AR that frees it from heat shock proteins that sequester AR in the cytoplasm. AR then translocates to the nucleus and binds to specific DNA sequences called androgen response elements that regulate gene expression (11). In the nonclassical pathway, androgen binding to AR in the cytoplasm or at the plasma membrane rapidly (within seconds to minutes) causes the activation of a set of protein kinases including Src, ERK, protein kinase A, Akt, and protein kinase C as well as expression of genes downstream (reviewed in Refs. 12 and 13). Androgens can also increase intracellular levels of inositol-1,4,5-triphosphate (IP3) and diacylglycerol as well as increase calcium influx and calcium-mediated cell signaling (14). In this issue of Endocrinology, Crabtree, Kilbourne, and colleagues (15) report the development of a mouse model that should permit characterization of the molecular mechanisms responsible for AGA. Specifically, transgenic mice were produced that express human AR under

Effect of intra-testicular melatonin injection on testicular functions, local and general immunity of a tropical rodent Funambulus pennanti

Local antigonadotrophic action of melatonin in testes has never been correlated with local and general immune status of any rodent. Intra-testicular injection of melatonin (2.5μg/50μl) for 10days (MI-10D) and 20days (MI-20D) was given to young adult male of Funambulus pennanti and testicular androgen receptor (AR), androgen binding protein (ABP) expression, 3β-hydroxysteroid dehydrogenase (3β-HSD) activity, and Mel1aR expression in thymus was checked along with general immune parameters. Further, immunohistochemical localization of Mel1aR in testes was done. Decreased AR, ABP expression, testes weight, 3β-HSD activity, testosterone level, and spermatogenesis but increased Mel1aR expression in thymus, immunoreactivity in testes, and testicular macrophages following injection was noted. Lymphatic tissue weight, leukocyte, lymphocyte count, lymphocyte proliferation in spleen, thymus, plasma melatonin, and IL-2 level increased in a duration-dependent manner following intra-testicular injection. Intra-testicular injection of melatonin decreased steroidogenesis by enhancing the primary effect of melatonin on Leydig cell endocrine function. Along with reduced circulatory testosterone production, an increase in testicular as well as general immunity was observed in a duration-dependent manner. Therefore, a local participation of melatonin in testes of F. pennanti to control testicular androgen production is suggested.

Camptothecin disrupts androgen receptor signaling and suppresses prostate cancer cell growth

The androgen receptor (AR) is the main therapeutic target for treatment of metastatic prostate cancers. The present study demonstrates that the topoisomerase I inhibitor camptothecin selectively inhibits androgen-responsive growth of prostate cancer cells. Camptothecin strikingly inhibited mutated and wild-type AR protein expression in LNCaP and PC-3/AR cells. This inhibition coincided with decreased androgen-mediated AR phosphorylation at Ser 81 and reduced androgen-mediated AR transcriptional activity in a dose-dependent manner. Additionally, camptothecin disrupted the association between AR and heat shock protein 90 and impeded binding of the synthetic androgen [ 3H]R1881 to AR in LNCaP cells. Camptothecin also blocked androgen-induced AR nuclear translocation, leading to downregulation of the AR target gene PSA. In addition to decreasing the intracellular and secreted prostate-specific antigen (PSA) levels, camptothecin markedly inhibited androgen-stimulated PSA promoter activity. Collectively, our data reveal that camptothecin not only serves as a traditional genotoxic agent but, by virtue of its ability to target and disrupt AR, may also be a novel candidate for the treatment of prostate cancer.

FKBP51 Promotes Assembly of the Hsp90 Chaperone Complex and Regulates Androgen Receptor Signaling in Prostate Cancer Cells

Prostate cancer progression to the androgen-independent (AI) state involves acquisition of pathways that allow tumor growth under low-androgen conditions. We hypothesized that expression of molecular chaperones that modulate androgen binding to AR might be altered in prostate cancer and contribute to progression to the AI state. Here, we report that the Hsp90 cochaperone FKBP51 is upregulated in LAPC-4 AI tumors grown in castrated mice and describe a molecular mechanism by which FKBP51 regulates AR activity. Using recombinant proteins, we show that FKBP51 stimulates recruitment of the cochaperone p23 to the ATP-bound form of Hsp90, forming an FKBP51-Hsp90-p23 superchaperone complex. In cells, FKBP51 expression promotes superchaperone complex association with AR and increases the number of AR molecules that undergo androgen binding. FKBP51 stimulates androgen-dependent transcription and cell growth, and FKBP51 is part of a positive feedback loop that is regulated by AR and androgen. Finally, depleting FKBP51 levels by short hairpin RNA reduces the transcript levels of genes regulated by AR and androgen. Because the superchaperone complex plays a critical role in determining the ligand-binding competence and transcription function of AR, it provides an attractive target for inhibiting AR activity in prostate cancer cells.

Androgen-Deprivation Therapy in Prostate Cancer and Cardiovascular Risk

Androgen-deprivation therapy (ADT) is a widely used treatment for prostate cancer. Recently, several studies have reported an association between ADT and an increased risk of cardiovascular events, including myocardial infarction and cardiovascular mortality.1–5 These reports have led to increased interest and discussion regarding the metabolic effects of ADT and its possible association with increased cardiovascular risk. In addition, likely as a result of these reports, internists, endocrinologists, and cardiologists are now being consulted regarding the evaluation and management of patients in whom ADT is being initiated. Most of these physicians are not aware of the possible effects of ADT on cardiovascular risk factors or the issues regarding ADT and cardiovascular disease. Therefore, this multidisciplinary writing group has been commissioned to review and summarize the metabolic effects of ADT, to evaluate the data regarding a possible relationship between ADT and cardiovascular events in patients with prostate cancer, and to generate suggestions regarding the evaluation and management of patients, both with and without known cardiac disease, in whom ADT is being initiated. The writing group emphasizes that the purpose of this advisory is strictly informative. This advisory should thus not be construed as dictating clinical practice or superseding the clinical judgment of physicians, and it should not be used for medicolegal purposes. Androgens, produced mainly in the testicles, stimulate prostate cancer cells to grow. Lowering androgen levels can eliminate prostate cancer cells that require androgens to survive.6 ADT reduces levels of androgens in circulation, with the goal of improving outcomes in men with prostate cancer. Gonadotropin-releasing hormone (GnRH) agonists (eg, leuprolide, goserelin, and triptorelin) currently are the most common form of ADT and have largely supplanted the use of bilateral orchiectomy. Antiandrogens (eg, flutamide and bicalutamide) are a form of prostate cancer therapy that blocks the binding of androgen to …

Membrane androgen receptors may mediate androgen reinforcement

Anabolic-androgenic steroid (AAS) abuse is widespread. Moreover, AAS are reinforcing, as shown by self-administration in rodents. However, the receptors that transduce the reinforcing effects of AAS are unclear. AAS may bind to classical nuclear androgen receptors (ARs) or membrane receptors. We used two approaches to examine the role of nuclear ARs in AAS self-administration. First, we tested androgen self-administration in rats with the testicular feminization mutation (Tfm), which interferes with androgen binding. If nuclear ARs are essential for AAS self-administration, Tfm males should not self-administer androgens. Tfm males and wild-type (WT) littermates self-administered the non-aromatizable androgen dihydrotestosterone (DHT) or vehicle intracerebroventricularly (ICV) at fixed-ratio (FR) schedules up to FR5. Both Tfm and WT rats acquired a preference for the active nose-poke during DHT self-administration (66.4+/-9.6 responses/4 h for Tfm and 79.2+/-11.5 for WT responses/4 h), and nose-pokes increased as the FR requirement increased. Preference scores were significantly lower in rats self-administering vehicle (42.3+/-5.3 responses/4 h for Tfm and 19.1+/-4.0 responses/4 h for WT). We also tested self-administration of DHT conjugated to bovine serum albumin (BSA) at C3 and C17, which is limited to actions at the cell surface. Hamsters were allowed to self-administer DHT, BSA and DHT-BSA conjugates for 15 days at FR1. The hamsters showed a significant preference for DHT (18.0+/-4.1 responses/4 h) or DHT-BSA conjugates (10.0+/-3.7 responses/4 h and 21.0+/-7.2 responses/4 h), but not for BSA (2.5+/-2.4 responses/4 h). Taken together, these data demonstrate that nuclear ARs are not required for androgen self-administration. Furthermore, androgen self-administration may be mediated by plasma membrane receptors.

Androgen-Deprivation Therapy in Prostate Cancer and Cardiovascular Risk: A Science Advisory From the American Heart Association, American Cancer Society, and American Urological Association: Endorsed by the American Society for Radiation Oncology

Androgen-deprivation therapy (ADT) is a widely used treatment for prostate cancer. Recently, several studies have reported an association between ADT and an increased risk of cardiovascular events, including myocardial infarction and cardiovascular mortality.1–5 These reports have led to increased interest and discussion regarding the metabolic effects of ADT and its possible association with increased cardiovascular risk. In addition, likely as a result of these reports, internists, endocrinologists, and cardiologists are now being consulted regarding the evaluation and management of patients in whom ADT is being initiated. Most of these physicians are not aware of the possible effects of ADT on cardiovascular risk factors or the issues regarding ADT and cardiovascular disease. Therefore, this multidisciplinary writing group has been commissioned to review and summarize the metabolic effects of ADT, to evaluate the data regarding a possible relationship between ADT and cardiovascular events in patients with prostate cancer, and to generate suggestions regarding the evaluation and management of patients, both with and without known cardiac disease, in whom ADT is being initiated. The writing group emphasizes that the purpose of this advisory is strictly informative. This advisory should thus not be construed as dictating clinical practice or superseding the clinical judgment of physicians, and it should not be used for medicolegal purposes. Androgens, produced mainly in the testicles, stimulate prostate cancer cells to grow. Lowering androgen levels can eliminate prostate cancer cells that require androgens to survive.6 ADT reduces levels of androgens in circulation, with the goal of improving outcomes in men with prostate cancer. Gonadotropin-releasing hormone (GnRH) agonists (eg, leuprolide, goserelin, and triptorelin) currently are the most common form of ADT and have largely supplanted the use of bilateral orchiectomy. Antiandrogens (eg, flutamide and bicalutamide) are a form of prostate cancer therapy that blocks the binding of androgen to …

Inhibition of glycogen synthase kinase‐3β promotes nuclear export of the androgen receptor through a CRM1‐dependent mechanism in prostate cancer cell lines

The androgen receptor (AR) is a ligand-dependent transcription factor belonging to the steroid hormone receptor superfamily. Under normal conditions, in the absence of a ligand, the AR is localized to the cytoplasm and is actively transported into the nucleus upon binding of androgens. In advanced prostate cancer (PCa) cell lines, an increased sensitivity to dihydrotestosterone (DHT), enabling the cells to proliferate under sub-physiological levels of androgens, has been associated with increased stability and nuclear localization of the AR. There is experimental evidence that the glycogen synthase kinase-3beta (GSK-3beta), a multifunctional serine/threonine kinase is involved in estrogen and AR stability. As demonstrated in the following study by immunoprecipitation analysis, GSK-3beta binds to the AR forming complexes in the cytoplasm and in the nucleus. Furthermore, inhibition of GSK-3beta activity by pharmacological inhibitors like the maleimide SB216761, the chloromethyl-thienyl-ketone GSK-3 inhibitor VI or the aminopyrazol GSK-3 inhibitor XIII in cells grown in the presence of DHT triggered a rapid nuclear export of endogenous AR as well as of green fluorescent AR-EosFP. The nuclear export of AR following GSK-3beta inhibition could be blocked by leptomycin B suggesting a CRM1-dependent export mechanism. This assumption is supported by the localization of a putative CRM1 binding site at the C-terminus of the AR protein. The results suggest that GSK-3beta is an important element not only in AR stability but also significantly alters nuclear translocation of the AR, thereby modulating the androgenic response of human PCa cells.

Etoposide induces growth arrest and disrupts androgen receptor signaling in prostate cancer cells

Androgen and androgen receptor (AR)-mediated signaling are crucial for the development of prostate cancer. The present study indicates that the topoisomerase II inhibitor etoposide strikingly inhibits androgen/AR-mediated cell growth and androgen-stimulated DNA synthesis in prostate cancer cells. Etoposide significantly repressed the AR mRNA and protein expression in a dose-dependent manner. Etoposide-mediated down-regulation of AR was associated with blocking androgen-induced AR translocation from cytoplasm into nucleus of cells. Additionally, etoposide disrupted the association of AR and heat shock protein 90 and impeded binding of the synthetic androgen [3H]R1881 to AR in LNCaP cells. Etoposide simultaneously reduced the intracellular and secreted PSA levels, a marker for the progression of prostate cancer. These findings collectively reveal that etoposide not only serves as a traditional genotoxic agent but directly targets AR as an AR disrupting therapeutic strategy in prostate cancer.

Immature rat seminiferous tubules reconstructed in vitro express markers of Sertoli cell maturation after xenografting into nude mouse hosts

Sertoli cells undergo a maturation process during post-natal testicular development that leads to the adult-type Sertoli cell, which is required for spermatogenesis. Understanding Sertoli cell maturation is therefore necessary to gain insight into the underlying causes of impaired spermatogenesis and male infertility. The present study characterized the cellular and molecular differentiation of Sertoli cells in a xenograft model of mammalian testicular development. Immature rat Sertoli cells were cultured in a three-dimensional culture system to allow the formation of cord-like structures. The in vitro Sertoli cell cultures were then grafted into nude mice. Sertoli cell proliferation, morphological differentiation and mRNA expression of Sertoli cell maturation markers were evaluated in xenografts. Sertoli cell proliferation significantly decreased between 1 and 4 weeks (6.7 +/- 0.9 versus 1.2+/- 0.1%, P < 0.001), and was maintained at low levels thereafter. Sertoli cell cord-like structures significantly decreased between 1 and 4 weeks (59.6 versus 21%, P < 0.05), whereas Sertoli cell tubules were more frequently observed after 4 weeks (13.3 versus 73.1%, P < 0.05). Furthermore, expression of androgen binding protein, transferrin and follicle stimulating hormone receptor, markers for mature Sertoli cells, was detected after 1 week of grafting and increased significantly thereafter. We conclude from these results that rat Sertoli cells continue maturation after xenografting to the physiological environment of a host. This model of in vitro tubule formation will be helpful in future investigations addressing testicular maturation in the mammalian testis.

Characterization of a high-affinity, low-capacity androgen binding protein in human term placental cytosol.

A high-affinity, low-capacity androgen binding component in human placental cytosol was characterized. (3H)-R1881, a synthetic androgen, was used as radioactive ligand for characterization and quantification of this placental androgen binding component. Various naturally occurring as well as synthetic steroids were first investigated for their in vitro stability under receptor assay conditions (i.e., an overnight incubation at 4 degrees C). Only the synthetic steroids were found to be metabolically stable. The rate constant of dissociation was found to be 6.42 X 10(-4) s-1 (on the basis of k-1 the rate constant of association was 1.27 X 10(5) M-1 s-1). The concentration of androgen binding protein was measured in 50 human term placentae. The mean concentration was 169 +/- 132 fmol/mg protein, and the average Kd was 5.07 +/- 2.2 X 10(-9) M. Placentae of female fetuses contained significantly higher concentrations (219 +/- 140 fmoles/mg protein) than those of male fetuses (115.2 +/- 101 fmoles/mg protein). The (3H)-R1881-androgen binding protein complex exhibited a sedimentation coefficient of 4S under low salt conditions. The binding site was only specific for androgens and progestins but not for steroids of other classes.

Identification of Intracisternal A-Particle Like Element as an FSH Regulated Transcript in Immature Rat Sertoli Cells

Sertoli cells under the influence of Follicle Stimulating Hormone are known to provide a microenvironment for the growth and differentiation of germ cells. Follicle Stimulating Hormone regulates proliferation of Sertoli cells only during the early neonatal period and during adult period it regulates functional parameters like Transferrin, Androgen binding protein and other factors needed for germ cell differentiation and how this is achieved is not known. In an attempt to understand the differential action of Follicle Stimulating Hormone on the Sertoli cells, we employed the approach of neutralization of endogenous Follicle Stimulating Hormone in neonatal rats for a very limited period and study the effect on the regulation of gene expression by Differential Display RT-PCR analysis. One of the transcripts was found to be down regulated following neutralization of endogenous Follicle Stimulating Hormone in the neonatal rats and it shared identity with Intracisternal A particle element, an endogenous retrovirus. Often integration of Intracisternal A particle into host genes and its regulation result in growth factor independence suggesting a role in proliferation. Interestingly, the expression of Intracisternal A particle transcript is not regulated by Follicle Stimulating Hormone in the adult rat Sertoli cells suggesting a possible reason for stimulation of proliferation of Sertoli cells by Follicle Stimulating Hormone only in the neonatal rats.

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.

Development of Androgen Receptor Antagonists with Promising Activity in Castration-Resistant Prostate Cancer

Androgen receptor (AR) continues to play a central role in prostate cancers that relapse after androgen deprivation therapy, but these tumors are refractory to available AR antagonists. In a recent issue of Science, Tran et al. describe an antagonist that prevents AR recruitment to chromatin and shows efficacy in relapsed prostate cancer.