The androgen receptor of the urogenital tract of the fetal rat is regulated by androgen

Specific morphogenetic events in mouse external genitalia sex differentiation are responsive/dependent upon androgens and/or estrogens

The objective of this study was to perform a comprehensive morphologic analysis of developing mouse external genitalia (ExG) and to determine specific sexual differentiation features that are responsive to androgens or estrogens. To eliminate sex steroid signaling postnatally, male and female mice were gonadectomized on the day of birth, and then injected intraperitoneally every other day with DES (200 ng/g), DHT (1 μg/g), or oil. On day-10 postnatal male and female ExG were dissected, fixed, embedded, serially sectioned and analyzed. We identified 10 sexually dimorphic anatomical features indicative of normal penile and clitoral differentiation in intact mice. Several (but not all) penile features were impaired or abolished as a result of neonatal castration. Those penile features remaining after neonatal castration were completely abolished with attendant clitoral development in androgen receptor (AR) mutant male mice (X(Tfm)/Y and X/Y AR-null) in which AR signaling is absent both pre- and postnatally. Administration of DHT to neonatally castrated males restored development of all 10 masculine features to almost normal levels. Neonatal ovariectomy of female mice had little effect on clitoral development, whereas treatment of ovariectomized female mice with DHT induced partial masculinization of the clitoris. Administration of DES to neonatally gonadectomized male and female mice elicited a spectrum of development abnormalities. These studies demonstrate that the presence or absence of androgen prenatally specifies penile versus clitoral identity. Differentiated penile features emerge postnatally and are sensitive to and dependent upon prenatal or pre- and postnatal androgen. Emergence of differentiated clitoral features occurs postnatally in either intact or ovariectomized females. It is likely that each penile and clitoral feature has a unique time-course of hormonal dependency/sensitivity.

Prenatal androgen exposure leads to alterations in gene and protein expression in the ovine fetal ovary

Exposure of a female fetus to increased androgens in utero results in an adult phenotype reminiscent of polycystic ovary syndrome. We investigated whether prenatal androgens could directly alter the structure and function of the fetal ovary. We examined fetal ovarian cell proliferation, germ cell volume, and the expression of steroid receptors and steroidogenic enzymes. In addition, we studied the inhibitors of differentiation (Ids) and the SLIT/Roundabout developmental pathways. Female fetuses were collected from ewes treated with 100 mg testosterone propionate (TP) or vehicle control (C), twice weekly from d 60 to 70 (C = 3, TP = 6) or d 90 (C = 6, TP = 8). Female fetuses were also collected at d 70 after a single injection of TP (20 mg) or vehicle C into the fetal flank at d 60 (C = 4, TP = 8). Prenatal androgenization had no effect on fetal ovarian morphology, cell proliferation, or germ cell volume. However, there was a reduction in the expression of StAR, CYP11A, CYP17, and LHR at d 90 of gestation. There was also an increase in Id1 immunostaining at d 90 and an increase in Id3 immunostaining at d 70. Direct injection of TP into the fetus down-regulated ovarian CYP11A, estrogen receptor α and β mRNA, and ROBO1 and up-regulated CYP19, androgen receptor immunostaining, and Id3 mRNA and protein. Although at d 90 prenatal androgenization does not result in structural changes of the fetal ovary, there are functional changes that may impact on ovarian development. TP has direct actions on the fetal ovary, and these may contribute to the adult ovarian phenotype in the ovine model of polycystic ovary syndrome.

Role of hormones, genes, and environment in human cryptorchidism

Cryptorchidism is the most frequent congenital birth defect in male children (2-4% in full-term male births), and it has the potential to impact the health of the human male. In fact, although it is often considered a mild malformation, it represents the best-characterized risk factor for reduced fertility and testicular cancer. Furthermore, some reports have highlighted a significant increase in the prevalence of cryptorchidism over the last few decades. Etiology of cryptorchidism remains for the most part unknown, and cryptorchidism itself might be considered a complex disease. Major regulators of testicular descent from intraabdominal location into the bottom of the scrotum are the Leydig-cell-derived hormones testosterone and insulin-like factor 3. Research on possible genetic causes of cryptorchidism has increased recently. Abundant animal evidence supports a genetic cause, whereas the genetic contribution to human cryptorchidism is being elucidated only recently. Mutations in the gene for insulin-like factor 3 and its receptor and in the androgen receptor gene have been recognized as causes of cryptorchidism in some cases, but some chromosomal alterations, above all the Klinefelter syndrome, are also frequently involved. Environmental factors acting as endocrine disruptors of testicular descent might also contribute to the etiology of cryptorchidism and its increased incidence in recent years. Furthermore, polymorphisms in different genes have recently been investigated as contributing risk factors for cryptorchidism, alone or by influencing susceptibility to endocrine disruptors. Obviously, the interaction of environmental and genetic factors is fundamental, and many aspects have been clarified only recently.

Androgenic dependence of exophytic tumor growth in a transgenic mouse model of bladder cancer: a role for thrombospondin-1

BACKGROUND

Steroid hormones influence mitogenic signaling pathways, apoptosis, and cell cycle checkpoints, and it has long been known that incidence of bladder cancer (BC) in men is several times greater than in women, a difference that cannot be attributed to environmental or lifestyle factors alone. Castration reduces incidence of chemically-induced BC in rodents. It is unclear if this effect is due to hormonal influences on activation/deactivation of carcinogens or a direct effect on urothelial cell proliferation or other malignant processes. We examined the effect of castration on BC growth in UPII-SV40T transgenic mice, which express SV40 T antigen specifically in urothelium and reliably develop BC. Furthermore, because BC growth in UPII-SV40T mice is exophytic, we speculated BC growth was dependent on angiogenesis and angiogenesis was, in turn, androgen responsive.

METHODS

Flat panel detector-based cone beam computed tomography (FPDCT) was used to longitudinally measure exophytic BC growth in UPII-SV40T male mice sham-operated, castrated, or castrated and supplemented with dihydrotestosterone (DHT). Human normal bladder and BC biopsies and mouse bladder were examined quantitatively for thrombospondin-1 (TSP1) protein expression.

RESULTS

Mice castrated at 24 weeks of age had decreased BC volumes at 32 weeks compared to intact mice (p = 0.0071) and castrated mice administered DHT (p = 0.0233; one-way ANOVA, JMP 6.0.3, SAS Institute, Inc.). Bladder cancer cell lines responded to DHT treatment with increased proliferation, regardless of androgen receptor expression levels. TSP1, an anti-angiogenic factor whose expression is inhibited by androgens, had decreased expression in bladders of UPII-SV40T mice compared to wild-type. Castration increased TSP1 levels in UPII-SV40T mice compared to intact mice. TSP1 protein expression was higher in 8 of 10 human bladder biopsies of normal versus malignant tissue from the same patients.

CONCLUSION

FPDCT allows longitudinal monitoring of exophytic tumor growth in the UPII-SV40T model of BC that bypasses need for chemical carcinogens, which confound analysis of androgen effects. Androgens increase tumor cell growth in vitro and in vivo and decrease TSP1 expression, possibly explaining the therapeutic effect of castration. This effect may, in part, explain gender differences in BC incidence and implies anti-androgenic therapies may be effective in preventing and treating BC.

SEX STEROID HORMONE RECEPTORS IN THE DEVELOPING FEMALE REPRODUCTIVE TRACT OF LABORATORY RODENTS

Many chemicals released into the environment potentially disrupt the endocrine system in wildlife and humans. Some of these chemicals exhibit estrogenic activity by binding to the estrogen receptors. The developing organism is particularly sensitive to estrogenic chemicals during the critical period in which the induction of long-term changes and persistent molecular alterations in female reproductive tracts occur. Perinatal mouse and rat models can be utilized as indicators for determining the consequences of exposure to exogenous estrogenic agents, including possible xenoestrogens or environmental endocrine disruptors. Estrogen receptors (ER) and estrogen responsive genes, therefore, need to be identified in order to understand the molecular basis of estrogenic actions. Recent identifications of ER subtypes and isoforms make understanding target organ responses to these estrogenic chemicals even more difficult. Indeed, many reports suggest that these chemicals do affect the reproductive and developmental processes of female laboratory rodents that had been perinatally exposed, and that interactions between sex steroid hormone receptors occur. Much information concerning the expression of sex steroid receptors in rodents has been reported concerning the normal development of the Müllerian duct. Thus, accumulated information on the expression of ER subtypes and isoforms as well as that of progesterone and androgen receptors in laboratory rodents is herein reviewed, in addition to the presentation of our own data.

Effect of oral intake of dibutyl phthalate on reproductive parameters of Long Evans rats and pre-pubertal development of their offspring

To investigate the influence of dibutyl phtalate (DBP) given in a soy-free rat chow on pre-pubertal development, 46 Long Evans female rats 2-month-old were divided into three experimental groups and fed three different chows: (1) control; (2) DP 0.61 g/kg chow (12 mg/kgrat/day); (3) DP 2.5 g/kg chow (50 mg/kg rat/day) for 2 months. While under this treatment, they were mated and their offspring studied. Litter size and female:male ratio were recorded. At 14 days of age 6, male pups of each group were sacrificed and testis and thymus were excised and weighed. Pups were weaned at 22 days of age and continued into three experimental groups according to diet. From day 22 onwards, vaginal opening, occurrence of first estrous, and pre-putial separation were recorded.

RESULTS

The percent of pregnancies showed a marked decrease in group 3, while no difference was observed between groups 1 and 2. Sex prevalence and litter size were not affected by the different diets. Pup survival showed a decrease when mothers were fed diet 2, but it was similar in diets 1 and 3. Pup weights on day 2 showed an evident (P < 0.05) reduction in groups 2 and 3, the decrease being more marked (P < 0.001) in group 3. On day 6, pups of group 2 showed lower weights (P < 0.01) as compared with the other groups. Weight gain was significantly higher in pups of group 3. Eye opening was not affected by the different diets. Fourteen-day-old male pups' relative weight of thymus and testis showed a decrease in animals whose mothers had been fed diets 2 and 3. Vaginal opening and occurrence of first estrous showed an evident delay (P < 0.05; P < 0.01) in females fed diets 2 and 3. Significant differences (P < 0.001) in pre-putial separation were observed between treated and untreated groups.

CONCLUSION

Offspring pre-pubertal development seems to be affected by oral intake of DBP by their mothers during pregnancy, the effects being more evident in the reproductive development of male pups.

Molecular and genetic regulation of testis descent and external genitalia development

Testicular descent as a prerequisite for the production of mature spermatozoa and normal external genitalia morphogenesis, and therefore facilitating copulation and internal fertilization, are essential developmental steps in reproduction of vertebrate species. Cryptorchidism, the failure of testis descent, and feminization of external genitalia in the male, usually in the form of hypospadias, in which the opening of the urethra occurs along the ventral aspect of the penis, are the most frequent pediatric complications. Thus, elucidating the molecular mechanisms involved in the regulation of testis descent and the formation of external genitalia merits a special focus. Natural and transgenic rodent models have demonstrated both morphogenic processes to be under the control of a plethora of genetic factors with complex time-, space-, and dose-restricted expression pattern. The review elucidates the molecular mechanisms involved in the regulation of testis descent and the formation of external genitalia and, wherever possible, assesses the differences between these rodent animal models and other mammalian species, including human.

Effect of organochlorine pesticides on human androgen receptor activation in vitro

Many persistent organochlorine pesticides (OCs) have been implicated in adverse effects, that is, reproductive and developmental effects, in man and in wildlife alike. It has been hypothesized that these so-called xeno-hormones could be responsible for the increased incidence in various male sexual differentiation disorders such as hypospadias, cryptorchidism, low sperm counts and quality. In this report, OCs, called endocrine disrupters, were tested for their interaction with the androgen receptor. The stable prostatic cell line PALM, which contains a human androgen receptor (hAR) expression vector and the reporter MMTV-luciferase, was used to characterize the response of hAR to OC and was compared with synthetic androgen compound R1881. We found that all the OC pesticides tested were able to shift the agonist [(3)H]-R1881 from its binding site to the AR in competitive binding assays. In addition, these compounds antagonize-in a dose-dependent manner-the AR-mediated transcription by synthetic AR ligand R1881. None of the pesticides reacted as agonists. These results demonstrate that OC endocrine activities in vivo probably result from direct and specific binding to the AR ligand-binding domain. Although the antagonistic potential of OC pesticides is lower than that of hydroxyflutamide, they are capable of disrupting the male hormone signaling pathway. Because these chemicals are extremely persistent and tend to bioaccumulate, these results support the hypothesis that the recent increase in the incidence of male sexual disorders could be due to long exposure to ubiquitous OC pesticides found in the environment.

Effects of perinatal simultaneous exposure to tributyltin (TBT) and p,p'-DDE [1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene) on male offspring of Wistar rats

p,p'-DDE [1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene; DDE] and tributyltin (TBT) are ubiquitous in the environment and in Japan were shown to bioaccumulate in marine products. Thus these chemicals serve as a source of contaminant in the mammalian food chain. Fetuses and neonates through maternal ingestion may be exposed to DDE and TBT. Therefore, the effects of concurrent exposure to DDE and TBT were investigated in male Wistar rat offspring of dams ingesting these two contaminants. In this study, TBT suppressed the growth and delayed eye opening. However, both growth retardation and delayed eye opening produced by TBT failed to occur in the presence of DDE. Unexpectedly, the prostate weight of male rat offspring was significantly reduced with the administration of TBT but restored in the presence of DDE. These results indicate that TBT and DDE affected the development of male rat offspring following maternal exposure, and simultaneous administration of DDE prevented some of the observed effects of TBT, especially of an antagonistic nature, through a mechanism, still to be determined.

Androgens and male fertility

Androgens play a crucial role in the development of male reproductive organs such as the epididymis, vas deferens, seminal vesicle, prostate and the penis. Furthermore, androgens are needed for puberty, male fertility and male sexual function. High levels of intratesticular testosterone, secreted by the leydig cells, are necessary for spermatogenesis. Intratesticular testosterone is mainly bound to androgen binding protein and secreted into the seminiferous tubules. Inside the sertoli cells, testosterone is selectively bound to the androgen receptor and activation of the receptor will result in initiation and maintenance of the spermatogenic process and inhibition of germ cell apoptosis. The androgen receptor is found in all male reproductive organs and can be stimulated by either testosterone or its more potential metabolite dihydrotestosterone. Severe defects of the androgen receptor may result in abnormal male sexual development. More subtle modulations can be a potential cause of male infertility. Treatment of an infertile man with testosterone does improve spermatogenesis, since exogenous administrated testosterone and its metabolite estrogen will suppress both GnRH production by the hypothalamus and Luteinising hormone production by the pituitary gland and subsequently suppress testicular testosterone production. Also, high levels of testosterone are needed inside the testis and this can never be accomplished by oral or parenteral administration of androgens. Suppression of testosterone production by the leydig cells will result in a deficient spermatogenesis, as can be seen in men taking anabolic-androgenic steroids. Suppression of spermatogenesis by testosterone administration is also the basis for the development of a male contraceptive. During cytotoxic treatment or irradiation suppression of intratesticular testosterone production cells may prevent irreversible damage to the spermotogonial stem cells.

Effects of in utero linuron exposure on rat Wolffian duct development

Linuron is an herbicide that displays weak androgen receptor antagonist activity. Male offspring exposed in utero to 50 mg/kg/day linuron often exhibit malformations in Wolffian duct derivatives (i.e. the epididymis and vas deferens). The objectives of this study were to determine the point during the perinatal period that linuron-induced epididymal lesions can be identified, to characterize linuron-mediated perinatal testicular and epididymal pathology, and to determine whether male rat fetuses exposed prenatally to linuron exhibit decreased intratesticular and serum testosterone (T) levels. Pregnant rats were administered corn oil vehicle or linuron by gavage at 0 or 50 mg/kg/day (n = 3 controls, 5-11 linuron-treated dams per time point) from gestation days (GD) 12 to 21 or to termination. Male fetuses or offspring were necropsied on GD 17, 19, and 21, and postnatal days (PND) 7 and 14. Epididymal malformations were not observed in fetuses from linuron-treated dams but were seen in linuron-exposed male offspring on PND 7 and 14. No testicular lesions were observed at any time point. The growth and development of linuron-exposed fetuses were altered, as evidenced by slight decreases in fetal weight and increased levels of immunoreactive proliferating cell nuclear antigen (PCNA) on GD 21. Intratesticular and serum T levels were not decreased in linuron-exposed male fetuses. These findings indicate that the adversely altered adult phenotype following in utero exposure to linuron is very similar to that produced by the antiandrogens di-n-butyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP). However, the absence of testicular lesions or alterations in fetal testosterone levels would suggest that the effect of linuron on the developing Wolffian ducts is distinctly different from DBP or DEHP.

Hormonal control of gubernaculum development during testis descent: gubernaculum outgrowth in vitro requires both insulin-like factor and androgen

The gubernaculum connects the gonad to the inguinoscrotal region and is involved in testis descent. It rapidly develops in the male fetus, whereas development in the female fetus is lacking. Possible factors involved in gubernaculum development are androgens, anti-Müllerian hormone (AMH), and insulin-like factor (Insl3). Sexual dimorphism in gubernaculum development correlated with the mitotic activity of cells in the gubernacular bulbs from male and female fetuses. Androgen receptor expression was restricted to the mesenchymal core of the gubernacular bulb, whereas skeletal muscle was detected in its outer layer. In an organ culture system devised to further study gubernaculum development in vitro, morphology of gubernacular explants grown in the presence of testes was comparable with that of gubernacula developed in vivo. Testicular tissue or medium containing R1881, a synthetic androgen, had a growth stimulatory effect on gubernacular explants compared with ovarian tissue or basal medium only. Moreover, Amh-/-, Amh+/-, and Insl3+/- testes stimulated the growth of gubernacular explants to the same extent as control testes. Insl3-/- testes, however, did not produce such an activity. This study reveals an essential role for both androgen and Insl3 in the gubernaculum outgrowth during transabdominal testis descent.

Neural androgen receptor regulation: effects of androgen and antiandrogen

Androgens exert profound effects on the organization and function of the central nervous system. These effects are mediated by the androgen receptor (AR), a ligand-dependent transcription factor. The mechanisms of AR regulation in neural tissue, however, remain to be fully elucidated. Characterizing this process can provide important information regarding receptor function and AR gene regulation in the brain. Previously, it was shown that testosterone (T) up-regulated neural AR in a dose-dependent manner in both male and female mice. In the present study, whether AR was differentially regulated by the natural agonists T and dihydrotestosterone (DHT) or the nonsteroidal antagonist flutamide (FLU) was assessed. Males were gonadectomized and AR levels were allowed to decline to baseline 3 days after surgery. Changes in AR protein content produced by the various treatments were measured by semiquantitative Western blot of limbic system extracts. Treatment with T or DHT significantly augmented AR 3 and 7 h after hormone administration, but only DHT sustained this increase for 21 h. This difference also was observed when males were given T plus finasteride (FIN, a 5alpha reductase inhibitor). The findings demonstrate that the two endogenous ligands have differential time course effects on neural AR. The antiandrogen FLU failed to up-regulate AR at doses up to 100 times higher than T or DHT. When administered concomitantly with T or DHT, it effectively inhibited the augmentation of AR normally seen 3 h after androgen treatment. While immunohistochemical studies showed that FLU was able to promote nuclear translocation of AR, Western analysis revealed that FLU, in contrast to T and DHT, failed to maintain the integrity of AR. The results demonstrate that (a) the endogenous androgens T and DHT regulate AR differently, suggesting a potential cellular mechanism that may contribute to the difference in neural target gene sensitivity to these androgens; (b) up-regulation of AR occurs only in the presence of agonists; (c) the mechanism of action of FLU in the brain involves inhibition of AR protein up-regulation normally seen in response to androgen; and (d) FLU promotes AR nuclear translocation but not augmentation of cellular AR populations. These findings demonstrate that in vivo AR regulation in the brain basically parallels mechanisms proposed from results obtained with transfected cells and cell lines.

Disruption of androgen-regulated male reproductive development by di(n-butyl) phthalate during late gestation in rats is different from flutamide

Gestational and lactational exposure to di(n-butyl) phthalate (DBP) at >/=250 mg/kg/day disrupts male rat reproductive development and function. Although this indicates an antiandrogenic mechanism, DBP and its biologically active metabolite do not interact with the androgen receptor (AR) in vitro. In the present study, we compared the effects of DBP and the antiandrogen flutamide using a shorter exposure during the prenatal period of male sexual differentiation in rats. Pregnant CD rats received DBP at 0, 100, 250, or 500 mg/kg/day po (n = 10) or flutamide at 100 mg/kg/day po (n = 5) from Gestation Days 12 to 21. In F1 males, DBP (500 mg/kg/day) and flutamide caused hypospadias; cryptorchidism; agenesis of the prostate, epididymis, and vas deferens; degeneration of the seminiferous epithelium; and interstitial cell hyperplasia of the testis. Flutamide and DBP (250 and 500 mg/kg/day) also produced retained thoracic nipples and decreased anogenital distance. Interstitial cell adenoma occurred at 500 mg DBP/kg/day in two males. The only effect seen at 100 mg DBP/kg/day was delayed preputial separation. In contrast to flutamide, DBP caused a low incidence of prostate agenesis and hypospadias with no vaginal pouch. The low incidence of DBP-induced intraabdominal testes contrasted with the high incidence of inguinal testes seen with flutamide. Thus prenatal male sexual differentiation is a sensitive period for the reproductive toxicity of DBP. A no observed adverse effect level was not established and the lowest observed (adverse) effect level was 100 mg/kg/day. Flutamide and DBP disrupted the androgen signaling necessary for male sexual differentiation but with a different pattern of antiandrogenic effects. DBP is an example of an environmental antiandrogen that disrupts androgen-regulated male sexual differentiation without interacting directly with the AR, as does flutamide.

Developmental expression of the androgen receptor during virilization of the urogenital system of a marsupial

In the marsupial tammar wallaby, virilization begins approximately 3 wk after the onset of testosterone synthesis. In the eutherian mammal, in contrast, the onset of virilization of the male urogenital tract occurs shortly after the onset of androgen synthesis. Androgen action requires the presence of the androgen receptor to mediate a response in target tissues. We therefore investigated the developmental expression of the androgen receptor (AR) in both sexes of the tammar wallaby. AR gene transcript was detected in fetal gonad and brain as early as Day 19 of the 26.5-day gestation, 7 days earlier than the first rise in testicular testosterone (Days 0-5 postpartum [p.p.]). Immunoreactive AR was identified in the male urogenital sinus (UGS) 2 days before birth and in the female UGS and mammary glands by the day of birth. AR was present in the UGS, vagina, and prostate until Day 152 p.p., the oldest age examined. AR was identified in the gubernaculum testis at Day 2 p.p. and became more abundant by Day 32. In the phallus of both sexes, AR was identified by Day 4 p.p. and until Day 157, the oldest age examined. AR was not detected in the scrotum at any age from the day of birth to Day 157. Maturation of the phallus, wolffian duct, and epididymis was marked by appearance of epithelial immunostaining. AR was localized in the epithelium of the UGS in females by Day 50 p.p. but was not found in the epithelium of the male UGS up to Day 152 p.p., the oldest examined. AR were found in the mesenchyme of the UGS of male and female tammars 3-4 wk before virilization is first evident in the male at Day 25 p.p. We conclude that the presence of AR is not the initiating signal for virilization of the UGS in this marsupial male.

Androgen receptor gene alterations are not associated with isolated cryptorchidism

PURPOSE

Multiple theories of testicular descent exist but there is no consensus. Cryptorchidism is a component of the androgen insensitivity syndrome, suggesting that testicular descent may be at least partially under the control of androgenic stimulation. To determine whether isolated cryptorchidism may be caused by androgen insensitivity, we screened a population of boys with isolated cryptorchidism for the presence of androgen receptor gene alterations.

MATERIALS AND METHODS

Deoxyribonucleic acid (DNA) was isolated from tissue collected from 21 patients with isolated cryptorchidism during orchiopexy. Patient selection was biased to maximize the likelihood of detection of a genetic etiology of cryptorchidism. The DNA was screened for androgen receptor gene alterations in exons 2 to 8 using single strand conformational polymorphism analysis.

RESULTS

No abnormalities in the androgen receptor gene were detected by single strand conformational polymorphism analysis in any patient.

CONCLUSIONS

Mutations of the androgen receptor gene in the hormone and DNA binding domains of the protein appear to be an unlikely cause of isolated cryptorchidism.

Androgen receptor gene alterations are not associated with isolated cryptorchidism

PURPOSE

Multiple theories of testicular descent exist but there is no consensus. Cryptorchidism is a component of the androgen insensitivity syndrome, suggesting that testicular descent may be at least partially under the control of androgenic stimulation. To determine whether isolated cryptorchidism may be caused by androgen insensitivity, we screened a population of boys with isolated cryptorchidism for the presence of androgen receptor gene alterations.

MATERIALS AND METHODS

Deoxyribonucleic acid (DNA) was isolated from tissue collected from 21 patients with isolated cryptorchidism during orchiopexy. Patient selection was biased to maximize the likelihood of detection of a genetic etiology of cryptorchidism. The DNA was screened for androgen receptor gene alterations in exons 2 to 8 using single strand conformational polymorphism analysis.

RESULTS

No abnormalities in the androgen receptor gene were detected by single strand conformational polymorphism analysis in any patient.

CONCLUSIONS

Mutations of the androgen receptor gene in the hormone and DNA binding domains of the protein appear to be an unlikely cause of isolated cryptorchidism.

Glucocorticoid receptor mRNA and protein in fetal rat lung in vivo: modulation by glucocorticoid and androgen

Pulmonary glucocorticoid receptor (GR) is essential to timely preparation for the onset of breathing air at birth. We have previously used primary culture of late-gestation fetal rat lung cells to demonstrate differential regulation of GR by glucocorticoid depending on cell type. In this study, we hypothesized that the action of glucocorticoid on GR mRNA expression and protein elaboration in lung cells might be modulated by interactions present in vivo but not in primary culture. Given that male sex hormone (androgen) has an inhibitory effect on antenatal lung development, we also postulated that androgen would decrease antenatal lung GR. We report that antenatal maternal injection of the glucocorticoid dexamethasone (1 mg/kg) enhanced fetal lung cellular levels of GR mRNA and protein as assessed by in situ hybridization and immunocytochemistry (ICC), respectively. ICC was performed using polyclonal rabbit anti-human antibody that reacts with rat GR whether bound to ligand or not and does not interfere with GR binding to DNA. Levels of GR mRNA and protein were enhanced in cells throughout all areas of the lung tissue, suggesting that interactions occurring in intact tissue may override the previously reported direct inhibition by glucocorticoid of GR protein elaboration in isolated fetal rat lung epithelial cells. Furthermore, antenatal administration of the androgen 5alpha-dihydrotestosterone (0.2 mg/kg) reduced tissue levels of GR mRNA and protein, consistent with androgenic inhibition of antenatal lung development by decreasing GR. We conclude that glucocorticoids and androgens exert opposite effects on fetal lung GR.

Androgen receptor mRNA detection in the human foetal prostate

In order to get an insight into androgen-mediated differentiation and development of the prostate, we detected the androgen receptor (AR) mRNA in the urogenital sinus of human foetuses at 12 and 16 weeks of gestation. Cytoplasmic dot hybridization using radiolabelled cDNA probe for human androgen receptor (AR) was performed. The AR mRNA could be detected at 12 weeks of gestation and its level was higher at 16 weeks of gestation.

The role of androgens in female vertebrates

The role of androgens in vertebrate females has been overlooked until recently. We examine the functional significance of androgens in females by reviewing studies that document relatively high levels of circulating plasma androgens, androgen receptors, or androgen-metabolizing enzymes in females. Among the mechanisms of androgenic action identified are enhanced neuron survival, stimulation of muscle satellite cell proliferation, alteration of ion current kinetics, and release of somatostatin. These mechanisms are not sex specific and thus we hypothesize that androgens play a significant role in normal female development. We encourage study in this nontraditional research area.

Expression and regulation of steroid 5 alpha-reductase in the genital tubercle of the fetal rat

The genital tubercle is a bipotential anlage that can develop into a penis or a clitoris. Formation of the penis requires synthesis within the tubercle of the androgen dihydrotestosterone by steroid 5 alpha-reductase isozymes. Isozyme 1 mRNA and protein were present in epithelial cells, whereas isozyme 2 transcripts were present in mesenchymal cells of developing genital tubercles from day 17, 19, and 21 rat embryos. These expression patterns were observed in both uncommitted anlagen and in committed male or female structures. Androgens did not significantly influence levels of 5 alpha-reductase mRNAs or affect their cellular distributions. Together with genetic data, the results implicate the mesenchyme as the crucial cell type in formation of the male external genitalia.

Androstenedione synergizes with stress or prenatal drug exposure to retard fetal growth: role of IGF

Pregnant Sprague-Dawley dams were implanted with a Silastic capsule (3 or 10 mm) containing androstenedione (AN) or cholesterol prior to being administered one of several treatments that create an endocrine profile of stress: maternal exposure to alcohol, pair feeding (PF), cocaine (COC), or restraint stress (RS). Controls (chow fed, CF) were left undisturbed during pregnancy. Treatments were administered from day 14 to day 22 of gestation. Fetuses were delivered by cesarean section on day 22. Results revealed that administration of AN to pregnant dams at a dose that does not influence fetal growth by itself can retard fetal growth in the presence of alcohol, PF, COC or RS. Data indicate that these effects are not directly attributable to changes in adrenocorticotropin (ACTH) or corticosterone levels. Preliminary results suggest a role for insulinlike growth factor (IGF) binding proteins (IGFBPs). Overall, these data demonstrate that AN can synergize with drugs and/or stress to enhance intrauterine growth retardation (IUGR). One underlying cause of this synergism between stress-related environmental events and androgenic actions on fetal growth may be increased expression of IGFBPs, which can sequester IGFs, thereby inhibiting their trophic actions on fetal and/or placental tissue.

Activation of androgen receptor in epidermal growth factor modulation of fetal mouse sexual differentiation

Previous studies from this laboratory indicated a role for epidermal growth factor (EGF) in androgen-dependent male sexual differentiation. The mechanism by which EGF modulates male sexual differentiation has not been determined and investigation has been made to assess the role for androgen receptor (AR) in mediating the EGF-induced effect. We report that EGF, like androgen, stabilized the Wolffian duct in the 13-day female specimen, grown in organ culture. Anti-AR, flutamide and cyproterone acetate blocked the Wolffian duct-stabilizing effect of EGF. EGF also induced cell proliferation of the fetal reproductive tract in a dose-dependent manner and a combination of physiological dosages of EGF and androgen-induced cell proliferation synergistically, suggesting an interactive effect of these two drugs. Cyproterone acetate blocked both EGF-induced normal cell proliferation and the synergistic cell proliferation induced by combination of EGF and androgen suggesting a role of AR in the effects of EGF. The role of AR was further assessed by determining the effect of EGF on AR binding directly. It was shown that EGF stimulated androgen binding activity of the male fetal reproductive tract cells significantly by increasing the number of binding sites by 3-fold with slight decrease in binding affinity. Thus, it appears that AR plays a role in mediating EGF-modulation of sexual differentiation.

Lack of feminization of the cremaster nucleus by prenatal flutamide administration in the rat and pig

PURPOSE

The sexually dimorphic cremaster nucleus contains motoneurons that project via the genitofemoral nerve and theoretically direct androgen dependent testicular descent. The effects of flutamide on descent and masculinization of the cremaster nucleus were studied in the rat and pig.

MATERIALS AND METHODS

Flutamide was given to pregnant rats and pigs on days 16 to 22 and 65 to 113 of gestation, respectively. Tissues were perfused and examined at birth (pigs) or at age 30 days (rats). Spinal cords were removed, sectioned and immunohistochemically stained for serotonin (rats) or substance P (pigs) to demarcate the position of the cremaster nucleus and allow the determination of cremaster motoneuron number.

RESULTS

After exposure to flutamide testes were undescended in 6 of 9 rats and 7 of 10 pigs. Cremaster motoneuron number per nucleus were 288 +/- 22 in control versus 250 +/- 27 in flutamide treated rats, and 165 +/- 28 in control versus 148 +/- 24 in flutamide treated pigs. The decrease in motoneuron number by flutamide was significant in both species (p < 0.02) but it did not approach the levels in female rats (93 +/- 11) and pigs (57 +/- 12). Cremaster motoneuron number did not correlate with testicular position. Porcine undescended testes were associated with a significant increase in mean gubernacular volume.

CONCLUSIONS

Unlike other sexually dimorphic spinal cord nuclei masculinization of the cremaster nucleus appears to be largely androgen independent and it does not correlate with ipsilateral testicular descent. These data suggest that androgens do not mediate descent of the testes via the efferent limb of the genitofemoral nerve.

A and B forms of the androgen receptor are expressed in a variety of human tissues

Human genital skin fibroblasts contain both the full-length 110 K androgen receptor protein (AR-B, apparent M(r) approximately 110,000) and an 87 K N-terminally truncated AR isoform (AR-A, apparent M(r) approximately 87,000). These two AR species are structurally analogous to the A- and B-isoforms of the progesterone receptor (PR). We examined the distribution pattern of human AR isoforms in a variety of fetal and adult tissues by Western blot analysis. Relative levels of immunoreactive AR proteins in high salt tissue extracts were estimated by densitometry in comparison to a standard normal genital skin fibroblast preparation. High AR levels (AR-A + AR-B = 0.8-7.7) were present in male and female reproductive tissues from mid-trimester fetuses, including penis, prostate, testis, epididymis, scrotal skin, labial skin, uterus/cervix, and ovary. AR-A and AR-B (0.08-0.9) also were found in 14 non-genital fetal tissues (bladder, fat, lung, great vessel, trachea, muscle, scalp skin, kidney, thyroid, intestine, thymus, ureter, stomach and rectum). AR-A accounted for 4-26% of the AR protein detected in these tissues. Ten other fetal tissues had low levels of AR-B (0.02-0.3) and little or no detectable AR-A. AR-B also was the predominant or only immunoreactive AR species found in 17 adult human tissues. AR levels in adult reproductive tissues (prostate, endometrium, ovary, uterus, fallopian tube, testis, seminal vesicle, myometrium, and ejaculatory duct) ranged from 0.1 to 2.2. Immunoreactive AR (0.4-0.8) also was present in specimens of prostate carcinoma, endometrial carcinoma, thyroid carcinoma and kidney. Lower levels of AR (0.03-0.1) were detected in adult breast, colon, lung and adrenal gland specimens. This study demonstrates that immunoreactive AR protein is present in a wide variety of human fetal and adult tissues and that two AR isoforms are expressed in many tissues.

17beta-Hydroxysteroid dehydrogenase 3 deficiency

Five known isoenzymes catalyze the 17beta-hydroxysteroid dehydrogenase reaction that controls the interconversion of estrone and estradiol and of testosterone and androstenedione. Mutations in the 17beta-hydroxysteroid dehydrogenase 3 gene impair the formation of testosterone in the fetal testis and give rise to genetic males with normal male Wolffian duct structures but female external genitalia. Such individuals are usually raised as females but virilize at the time of puberty as the result of a rise in serum testosterone. The 14 mutations characterized to date in 17 affected families include 10 missense mutations, 3 splice junction abnormalities, and 1 frame shift mutation. Three of the mutations have occurred in more than 1 family. The usual mechanism for testosterone formation in affected individuals at puberty appears to be conversion of androstenedione to testosterone in extraglandular tissues by one or more of the unaffected 17beta-hydroxysteroid dehydrogenase isoenzymes.

Developmental pattern and regulation by androgens of androgen receptor expression in the urogenital tract of the rat

Distribution and regulation of androgen receptor expression during fetal and neonatal virilization of the rat fetus was assessed by immunohistochemistry. In mesonephric duct derivatives the androgen receptor expression became evident first in the efferent ductules and epididymis (on fetal day 14), subsequently in the vas deferens and finally in the seminal vesicle. Mesenchymal cells of the urogenital tubercle were positive for androgen receptors from fetal day 14 onwards. In the mesenchymal cells of the prostate anlagen, androgen receptor positive cells were found first on fetal day 16. Administration of 5alpha-dihydrotestosterone to pregnant rats from day 11 to day 20 of gestation caused a stabilization of the wolffian duct in female fetuses. The androgen receptor expression pattern became similar as found in mail fetuses, and showed an increase in density and in frequency of androgen receptor positive cells. Administration of the androgen antagonist flutamide during the same interval caused a reduction in density and frequency of androgen receptor positive cells in male fetuses. These findings indicate that androgens enhance the expression of androgen receptors in the developing rat genital tract by induction of androgen receptor positive cells, and by increasing the frequency. The developmental pattern of androgen receptor expression in the rat mesonephric duct system reflects the androgen-responsiveness of the ducts, and is consistent with induction of the androgen receptor along the ducts by testosterone reaching these structures in an exocrine fashion.

Decreased immunoreactive androgen receptor levels are not the cause of isolated hypospadias

OBJECTIVE

To elucidate whether diminished levels of androgen receptor (AR) are the underlying cause for the development of hypospadias by determining AR levels in the foreskins of boys with hypospadias.

PATIENTS AND METHODS

The content of AR was determined by a sensitive immunoblotting technique in extracts from preputial tissue obtained from 15 patients (mean age 2.5, SD +/- 1.5 years) with hypospadias and from seven controls (mean age 2.5, SD +/- 1.5 years). Immunoreactivity of the protein was measured by densitometry.

RESULTS

No significant difference in mean AR content was found between those boys with hypospadias (2.1 +/- 0.9 fmol/mg protein, +/- SD) and the age-matched control group (2.2 +/- 0.3 fmol/mg protein). Stratification by the severity of hypospadias (distal and proximal on the shaft, and penoscrotal hypospadias) showed that the severity was not related to tissue AR levels.

CONCLUSION

It is unlikely that hypospadias is caused by a decreased expression of AR.

Isolation of differentially expressed sequence tags from steroid-responsive cells using mRNA differential display

Transcriptional control of steroid-regulated gene networks by nuclear receptor proteins results in the coordinate expression of a limited number of target genes. Although much is known about the structure and function of steroid receptors, relatively few cell-specific steroid-regulated genes have been isolated and characterized. In this paper we describe results using mRNA differential display reverse transcriptase PCR (DDPCR) to identify and isolate short cDNA sequence tags from thymocyte and prostate cells under various hormone conditions. Using this technique we have isolated several differentially expressed sequence tags (DESTs) from the mouse thymocyte cell line WEHI 7.2. Two of these DESTs, GIG10 and GIG18, are rapidly induced by dexamethasone within 2 h of treatment. GIG10 is a novel sequence and GIG18 is the mouse homologue of a human expressed sequence tag isolated from activated B lymphocytes. We also used DDPCR to isolate DESTs from androgen-modulated rat ventral prostate tissue, one of which we characterized and found to correspond to the 3' end of prostatic spermine binding protein mRNA, a known androgen-regulated gene. Modifications of the original DDPCR protocol, which we found can potentially decrease the frequency of isolating false-positive DESTs, are described and the merits of DDPCR, relative to other differential cDNA cloning strategies, are discussed.