Effects of hypophysectomy and prolactin replacement therapy on prostatic response to androgen in orchiectomized rats

The effects of hypophysectomy and prolactin replacement therapy on prostatic response to androgen in orchiectomized rats were studied. Castration 23 days prior to treatment with testosterone propionate (TP), followed by hypophysectomy 13 days before TP treatment, and then treatment with 1 mg TP every other day for 16 days caused a greater decrease in body weight, prostatic weight, and the level of citric acid in the prostate than did TP treatment, castration, and sham hypophysectomy. This suggests the existence of a pituitary factor in the maintenance of prostatic integrity. Prolactin replacement therapy in hypophysectomized, castrated,TP-treated rats significantly (p less than .005) increased the prostatic weight and both the content and concentration of citric acid. The results confirm previously reported observations that the prostatic response to androgens is markedly reduced by hypophysectomy in castrated rats, and that prolactin acts synergistically wtih testosterone in promoting prostatic growth and the concentration of citric acid in the prostate. The direct effects of both hypophysectomy and prolactin replacement therapy on the ventral and dorsolateral lobes of the prostate were also demonstrated.     

Influence of gender and the endocrine environment on the distribution of androgen receptors in the lacrimal gland

Androgens are known to regulate both the structure and function of lacrimal tissue in a variety of species. To explore the endocrine basis for this hormone action, the following study was designed to: (1) determine the cellular distribution of androgen receptors in the lacrimal gland; and (2) examine the influence of gender and the endocrine environment on the glandular content of these binding sites. Lacrimal glands were obtained from intact, castrated, hypophysectomized, diabetic or sham-operated male or female adult rats, mice or hamsters, as well as from orchiectomized rats exposed to placebo compounds or physiological levels of testosterone. The cellular location of androgen receptors was evaluated by utilizing an immunoperoxidase protocol, in which a purified rabbit polyclonal antibody to the rat androgen receptor was used as the first antibody. Our findings with lacrimal glands showed that: (1) androgen receptors are located almost exclusively in nuclei of epithelial cells; (2) the cellular distribution or intranuclear density of these binding sites is far more extensive in glands of males, as compared to females; (3) orchiectomy or hypophysectomy, but not sham-surgery or diabetes, lead to a dramatic reduction in the immunocytochemical expression of androgen receptors; and (4) testosterone administration to orchiectomized rats induces a marked increase in androgen receptor content, relative to that in placebo-exposed glands. Our results also reveal that a 10 kb androgen receptor mRNA exists in the rat lacrimal gland. Overall, these findings demonstrate that gender and the endocrine system may significantly influence the distribution of androgen binding sites in rat lacrimal tissue. Moreover, our results show that androgens up-regulate their own lacrimal gland receptors.     

Stromal development in the ventral prostate, anterior prostate and seminal vesicle of the rat

The prostate and seminal vesicle (SV) are androgen-dependent secretory glands of the male genital tract. They produce the bulk of the seminal secretions. The object of the present study was to examine and document the ontogeny of stromal maturation in the rat anterior and ventral prostate and SV. These organs have a loosely organized cellular mesenchyme during fetal development. During prostatic development the mesenchyme condensed to form smooth muscle sheaths immediately surrounding the epithelium, with looser connective tissue between individual ducts. In the SV, a loose connective tissue layer called the lamina propria lies between the epithelium and developing muscle. Smooth muscle alpha-actin, myosin, desmin, laminin, vinculin, vimentin and androgen receptor (AR) expression were examined by immunocytochemical methods during the pre- and postnatal developmental periods. The first marker to be detected was vimentin, which was initially found throughout the mesenchyme. During development vimentin became mostly restricted to the interductal tissue of the prostate and the lamina propria of the SV. Smooth muscle markers were expressed in an orderly sequence in a proximal to distal manner along prostatic ducts, from the urethra towards the tips. Expression of alpha-actin was followed by vinculin, myosin, desmin, and laminin. These markers became localized to the developing smooth muscle sheaths and were not expressed in the interductal tissue of the prostate or the lamina propria of the SV. Organ culture experiments demonstrated that androgens were required for the differentiation of smooth muscle sheaths. Castration of adult rats demonstrated that androgens were required to maintain smooth muscle differentiation. In castrates, the stroma was relatively thicker but less dense than in intact animals. Following castration, expression of the smooth muscle markers was lost sequentially in the reverse order of their expression during development. In long-term castrates alpha-actin, vimentin and a small amount of vinculin were detected. AR were first detected in the urogenital sinus mesenchyme immediately surrounding the epithelium at 16 days of gestation. As development progressed expression of AR became more widespread, and postnatally was found throughout the mesenchyme. As maturation of smooth muscle occurred, stromal expression of AR became localized to the muscular sheath immediately surrounding the epithelium. In the prostate the interductal connective tissue displayed very low levels of AR expression. In the SV, AR were also observed in the lamina propria. In summary, stromal differentiation and dedifferentiation in the rat prostate and SV were found to be androgen-dependent processes with ordered sequential ontogenic expression of specific markers.     

Regional expression of transforming growth factor-alpha in rat ventral prostate during postnatal development, after androgen ablation, and after androgen replacement

The prostate is a highly heterogeneous organ, composed of different types of epithelial and stromal cells organized regionally along the ductal network. Although androgen-stimulated growth and maintenance of the prostate gland primarily involve epithelial cells, it is unclear whether all epithelial cells are androgen dependent. Moreover, the actions of androgens may not be direct; a number of polypeptide growth factors, including transforming growth factor-alpha (TGFalpha), are postulated to mediate androgen action in the rat prostate. In this investigation, using an immunohistochemical technique, we examined the cellular and regional expression of TGFalpha in the rat ventral prostate during postnatal development to adulthood. TGFalpha-immunopositive cells were located throughout the ductal epithelium from postnatal days 5-20. By day 45 and thereafter, regional variation in TGFalpha expression became apparent; epithelial cells in the proximal segment exhibited intense staining, whereas those in the distal segment exhibited negligible staining. These observations were coincident with increased serum testosterone concentrations at puberty. To understand the role of androgen in the expression of TGFalpha in the epithelial cells of the distal and proximal segments of the adult rat ventral prostate, androgen was withdrawn by castration, and testosterone subsequently was administered. Androgen receptor protein expression decreased after castration and reappeared after androgen replacement in both the distal and proximal segments. TGFalpha staining was negligible in epithelial cells of the distal segment of intact adult rats, became prominent by 7 days after castration, but then diminished after the administration of testosterone. Western blot analyses revealed the presence of a specific 30-kDa immunoreactive form of TGFalpha in rat ventral prostate, and its quantity reflected the staining intensities observed in the immunohistochemical studies. These results suggest that TGFalpha expression is negatively regulated by androgen in epithelial cells of the distal segment. In contrast, staining for TGFalpha in epithelial cells of the proximal segment did not change with castration or testosterone administration, suggesting that TGFalpha is not regulated by androgen in this region of the ventral prostate. In summary, TGFalpha expression is differentially regulated among epithelial cells localized in two different regions of the ventral prostate. We hypothesize that TGFalpha may function as a survival factor for epithelial cells which, as a consequence of its expression, become androgen independent and thus escape apoptotic cell death after androgen ablation.     

Identification of genes expressed in the rat prostate that are modulated differently by castration and Finasteride treatment

In mammals, testosterone and 5alpha-dihydrotestosterone (DHT) are the principal male hormones (androgens). Testosterone is the most abundant circulating androgen, and is converted in specific tissues to DHT by the 5alpha-reductase enzymes. Although each of these androgens binds to the same receptor protein (androgen receptor, AR), each exerts biologically distinct effects. Theories to explain the specific effects of testosterone and DHT have centered on kinetic differences of binding of androgens to the receptor or differences in the metabolic fates of the two hormones. In the current experiments, differential display PCR (ddPCR) was used to identify genes regulated differently by testosterone and DHT. Adult male rats were treated as follows: castrated, treated with Finasteride (an inhibitor of 5alpha-reductase) or left intact for ten days. RNA was prepared from the dissected prostates of these animals and used for ddPCR. Genes exhibiting four distinct patterns of regulation were observed among the mRNAs. Class 1 genes showed equivalent expression in intact and Finasteride-treated animals, but were absent in castrated animals (mRNAs D1, D2, D6, D10). Class 2 genes showed higher expression in intact animals, intermediate levels following Finasteride treatment, but were absent in castrated animals (mRNA D8). Two classes of gene were particularly intriguing: class 3 showed gene expression only in the intact animal (mRNA D7, D9) and class 4 showed increased gene expression following Finasteride treatment (mRNA D3). While the patterns observed for some of these genes (e.g. D8) suggest that the different biological effects of testosterone and DHT may be due to the lower affinity of the AR for testosterone and limiting tissue concentrations of androgen, our results also suggest that some genes expressed in the rat prostate may be regulated in fundamentally different ways in response to testosterone and DHT.     

Castration-induced apoptosis in the rat ventral prostate is associated with increased expression of genes encoding insulin-like growth factor binding proteins 2,3,4 and 5

Insulin-like growth factor binding proteins (IGFBPs) have recently been demonstrated to act as regulators of apoptosis in vitro in both prostate and breast cancer cell lines. We show here that gene expression of IGFBP-2,-3,-4 and -5 increase rapidly in the rat ventral prostate following castration. Increases in IGFBP mRNA levels were detectable by Northern blotting by 6 hours and reached 5 to 10 fold of control levels at 72 hours after castration. Apoptosis in the ventral prostate, as detected in situ by the TUNEL method, was also induced as early as 6 hours after castration. TRPM-2/clusterin, a gene known to be associated with involution of the prostate, was not detected in sham castrated controls but was expressed by 24 hours following androgen ablation. IGF-I mRNA levels increased to 160% of control values within 6 hours following castration, then decreased gradually over the next 72 hours to 35% of control. Affinity labelling experiments demonstrated that IGF-I receptor levels increased initially after castration with peak binding at 24 hours, then declined to levels lower than control. These results suggest that rapid induction of IGFBPs in the rat ventral prostate following androgen ablation may play a role in apoptosis and involution of the prostate gland.     

Telomerase is activated in the prostate and seminal vesicles of the castrated rat

Telomeres, the repetitive non-coding DNA sequences found at the ends of all eukaryotic chromosomes, shorten with each cell division. It has been proposed that telomere shortening may be the counting element of a mitotic clock that keeps track of cell divisions; with shortening to a critical length acting as a senescence signal underlying cellular aging. The enzyme telomerase functions to maintain telomere length, thus allowing unlimited cell division, and has been associated with cellular immortalization and cancer. Stem cells have large, perhaps unlimited, replicative capacities. Since these cells are potentially immortal, we reasoned that they might posses active telomerase. We therefore assayed for telomerase activity in the stem cell enriched pools of the androgen-depleted sex accessory tissues in the castrated male rat. Following castration, the ventral prostate and seminal vesicles of the rat involute, losing approximately 90% of their cells by 21 days. These residual glands persist, and are enriched for stem cells, being capable of fully regenerating these glands if testosterone is re-introduced into the animal. We assayed telomerase activity in extracts from normal, involuted, and regenerating ventral prostate and seminal vesicles. Normal glands were found to be telomerase negative, whereas telomerase activity appeared as these glands involuted following castration. Conversely, telomerase activity disappeared during testosterone-induced regeneration of these residual glands. These results provide strong evidence for the ability of androgen to negatively-regulate telomerase activity in stem cell populations of the rat ventral prostate and seminal vesicles. and represent the first in vivo model system for the modulation of telomerase activity.     

Androgen-dependent protein interactions within an intron 1 regulatory region of the 20-kDa protein gene

The 20-kDa protein gene is androgen regulated in rat ventral prostate. Intron 1 contains a 130-base pair complex response element (D2) that binds androgen (AR) and glucocorticoid receptor (GR) but transactivates only with AR in transient cotransfection assays in CV1 cells using the reporter vector D2-tkCAT. To better understand the function of this androgen-responsive unit, nuclear protein interactions with D2 were analyzed by DNase I footprinting in ventral prostate nuclei of intact or castrated rats and in vitro with ventral prostate nuclear protein extracts from intact, castrated, and testosterone-treated castrated rats. Multiple androgen-dependent protected regions and hypersensitive sites were identified in the D2 region with both methods. Mobility shift assays with 32P-labeled oligonucleotides spanning D2 revealed specific interactions with ventral prostate nuclear proteins. Four of the D2-protein complexes decreased in intensity within 24 h of castration. UV cross-linking of the androgen-dependent DNA binding proteins identified protein complexes of approximately 140 and 55 kDa. The results demonstrate androgen-dependent nuclear protein-DNA interactions within the complex androgen response element D2.     

Stimulation of nucleic acid and protein synthesis in the epididymis and accessory organs of the rat by testosterone

The metabolism of 3H-testosterone by the epididymis and accessory organs of adult male rats exposed continuously to microdoses of cyproterone acetate from subcutaneous capsules were studied. The major metabolite of 3H-testosterone in the epididymis, vas deferens and ventral prostate of control rat was dihydrotestosterone while the formation of androstanediol by these tissues was low. The highest percentage of DHT was formed by the ventral prostate and cauda epididymis. In rats exposed to cyproterone acetate for four months, the conversion of testosterone to DHT was inhibited in all the tissues but maximally in the ventral prostate and cauda epididymis. In these rats, the secretory function of the ventral prostate was normal while that of the epididymis was markedly decreased. These data are discussed based on the differential thresholds of androgens required to regulate the functions of the accessory organs.     

Development of an androgen receptor-null model for identifying the initiation site for androgen stimulation of proliferation and suppression of programmed (apoptotic) death of PC-82 human prostate cancer cells

Whether androgen regulates the proliferation and survival of androgen-responsive prostate cancer cells directly or indirectly via a paracrine pathway initiated in androgen receptor (AR)-expressing stromal cells is unknown. To resolve this issue, female mice heterozygous for the testicular feminized male loss of function mutation in their X-linked AR genes were cross-bred to T cell-defective homozygous male nude mice. Using a PCR-based restriction enzyme digestion method, the resulting AR/tfm, Nu/nu F1 hybrid females were identified and back-crossed to homozygous male nude mice to produce AR-null male nude mice lacking both AR and T-cell function. Androgen-responsive PC-82 human prostate cancers were xenografted into these AR-null versus AR-wild-type male nude mice. In both backgrounds, the cancer cells did not grow in nonandrogenized hosts. In contrast, PC-82 prostate cancer cells grew with identical characteristics (i.e., take rate, morphology, PSA expression, growth rate, and percentage of cell proliferating or dying) in androgenized hosts of both backgrounds. Likewise, in both backgrounds, androgen ablation of mice bearing growing PC-82 cancers resulted in the inhibition of proliferation and activation of programmed (apoptotic) cell death of the cancer cells. These results demonstrate that both the androgen-stimulated proliferation and the suppression of programmed cell death of PC-82 human prostate cancer cells are initiated by the AR pathway directly within these cancer cells themselves and do not involve initiation by AR-expressing stromal cells in a paracrine manner.     

Identification of an androgen-induced C3-P4 DNA binding protein in the cytosol of rat ventral prostate

A DNA binding protein C3-P4 was detected in the rat ventral prostate cytosol by gel retardation assay using a 32P-labeled 31 base pair synthetic oligomers (sequence deduced from the rat prostatic steroid binding protein C3-1 gene promoter -149 to -119) as a probe. The DNA binding activity of C3-P4 DNA binding protein is sequence specific, with preference for single strand and coding strand exclusive. This protein can be detected in many androgen target tissues and controlled well by androgen in the rat ventral prostate, we speculate that this DNA binding protein may function as an accessory factor to androgen receptor (AR) for the regulation of the C3-1 gene expression.     

Population density and social, territorial, and physiological measures in the gerbil (Meriones unguiculatus).

Conducted 2 experiments with 80 male and 80 female Mongolian gerbils reared from weaning to adulthood in 4 same-sex and 4 mixed-sex density conditions. Ventral gland marking was greatly affected by density and less so by sex in both same-sex and mixed-sex groups. In same-sex but not mixed-sex groups crowding depressed several social interaction measures as well as body, ventral gland, and testis weights. In the mixed-sex groups, paired males and females had heaviest adrenal glands, ventral glands, and marking scores, as well as the highest reproductive rate. Mixed-sex crowding did not depress either social or physiological measures as much as did same-sex crowding. Effects of crowding are discussed in the framework of an information overload concept. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Midline interhemispheric fusion associated with atypical callosal dysgenesis: a mild type of holoprosencephaly

Pubertal male Wistar rats were submitted to bilateral castration and killed 7 or 14 days later; an additional group of castrated rats was submitted to ultrasound stimulation of the ventral region lying above the accessory sex glands, for 20 min a day from the 7th to the 14th day postcastration. Control intact rats were age-matched to the different treated groups. Seminal vesicle growth and secretory activity were investigated on the basis of weight and fructose content, respectively. A progressive fall in seminal vesicle weight was observed over a period of 7 (83% decrease) to 14 (92% decrease) days following castration; ultrasound treatment beginning on the 7th day prevented this additional weight reduction. Castration caused also a marked decrease (50-60%) in the fructose content of the seminal vesicle and the ultrasound energy promoted a partial recovery of the secretory activity of the gland. The results revealed a direct ultrasound stimulation of the seminal vesicle secretory activity in pubertal rats deprived of testicular androgens.     

Testosterone acts as a prohormone to stimulate male copulatory behavior in male deer mice (Peromyscus maniculatus bairdi).

Determined the importance of reduced and aromatized metabolites of testosterone for male sexual behavior in 111 male castrated deer mice treated with 5-alpha reductase and aromatase inhibitors. In Exp I, testosterone propionate (TP) activation of male copulatory behavior was blocked by the administration of the 5-alpha-reductase inhibitor 4-androsten-3-17-beta-carboxylic acid (17BC). These treatments also prevented TP stimulation of seminal vesicles and ventral prostate gland weight. The inhibitory effects of 17BC were specific to testosterone, since 17BC did not prevent dihydrotestosterone propionate (DHTP) induction of male sexual behavior or seminal vesicles and ventral prostate gland weight increases. In Exp II, TP activation of male copulatory behavior was prevented by the administration of the aromatase inhibitor 1,4,6-androstatriene-3,17-dione (ATD). The ATD did not interfere with DHTP activation of male reproductive behavior. Also, TP and DHTP stimulation of accessory sex organ weight was not blocked by ATD. It is suggested that metabolism of testosterone to both 5-alpha-reduced androgens and estrogens is obligatory for testosterone to reliably stimulate male sexual behavior in castrated male deer mice. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Arimidex: a potent and selective fourth-generation aromatase inhibitor

Dehydroepiandrosterone-sulfate (DHEA-S), the main secretory product of the human adrenal, requires the presence of steroid sulfatase, 3 beta-hydroxysteroid dehydrogenase/delta 5-delta 4 isomerase (3 beta-HSD), 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD), 5 alpha-reductase, and aromatase to form the active androgen dihydrotestosterone (DHT) and the estrogens 17 beta-estradiol (E2) and 5-androst-ene-3 beta,17 beta-diol (delta 5-diol) in peripheral target tissues. Because humans, along with non-human primates are unique in having adrenals that secrete large amounts of DHEA-S, the present study investigated the tissue distribution of the enzymatic activity of the above-mentioned steroidogenic enzymes required for the formation of active sex steroids in the male and female rhesus monkey. Estrone and DHEA sulfatase activities were measured in all 25 tissues examined, and with the exception of the salivary glands, estrogenic and androgenic 17 beta-HSDs were present in all the tissues examined. The adrenal, small and large intestine, kidney, liver, lung, fat, testis, prostate, seminal vesicle, ovary, myometrium, and endometrium all possess the above-mentioned enzymatic activities, thus suggesting that these tissues could possibly form the biologically active steroids E2 and DHT from the adrenal precursor DHEA-S. On the other hand, the oviduct, cervix, mammary gland, heart, and skeletal muscle possess all the enzymatic activities required to synthesize E2 from DHEA-S. The present study describes the widespread tissue distribution of steroid sulfatase, 3 beta-HSD, 17 beta-HSD, 5 alpha-reductase, and aromatase activities in rhesus monkey peripheral tissues.(ABSTRACT TRUNCATED AT 250 WORDS)