Androgen receptors in the rat ventral prostate and their hormonal control

Autoregulation of androgen receptor protein and messenger RNA in rat ventral prostate is protein synthesis dependent

In order to investigate the role of protein synthesis in the testosterone regulation of androgen receptor (AR) levels, in vivo studies were undertaken using the ventral prostate gland from adult male rats castrated 24 h previously. Our results showed that testosterone (400 microg/100 g body weight) increased nuclear AR binding 1 h after administration, whereas the protein synthesis inhibitor cycloheximide (400 microg/100 g body weight) by itself did not alter AR binding. However, concomitant administration of testosterone and cycloheximide blocked the testosterone-induced nuclear AR accumulation after 1 h. To determine if changes in AR binding reflected changes in AR protein levels, immunocytochemical studies were conducted on individually dissected ventral prostatic ducts. Castration 24 h previously induced a decrease in nuclear AR immunostaining when compared to intact animals. Testosterone treatment restored the nuclear staining, particularly at the distal tips of the prostatic ducts. Cycloheximide alone did not change AR immunostaining when compared to castrated vehicle-treated rats, yet it significantly decreased the nuclear AR staining induced by testosterone. Our results suggest that AR is being newly synthesized during testosterone treatment. To determine if the effect of testosterone in the regulation of the AR protein was ultimately due to changes at the messenger RNA (mRNA) levels, steady-state AR mRNA levels were measured. Northern blot analysis of poly A+ mRNA preparations revealed that androgen withdrawal for 24 h increased AR mRNA and that testosterone treatment for 1 h did not alter these increased AR mRNA levels. The inhibition of protein synthesis by cycloheximide did not change AR mRNA, but, when cycloheximide was administered in conjunction with testosterone, AR mRNA levels were significantly decreased. In an attempt to relate these responses to changes in transcriptional activity, the transcription inhibitor actinomycin D was administered in vivo. Whereas simultaneous administration of testosterone and cycloheximide modified AR mRNA and AR protein levels, concomitant administration of testosterone with actinomycin D did not alter these levels. It is therefore unlikely that testosterone modifies the transcription of AR mRNA within 1 h after its administration. Collectively, these results suggest that protein synthesis is involved in the mechanism of testosterone-promoted AR regulation. This protein synthesis-dependent mechanism may be involved in the regulation of the stability and/or the translation of AR mRNA in the prostate.

Prostate gland: structure, functions and regulation

The prostate gland plays an important role in male reproduction. It secretes enzymes, lipids, amines and metal ions essential for the normal function of spermatozoa. Development, differentiation and maintenance of the prostate gland depend on steroid and peptide hormones. Beside hormones growth factors also regulate the prostate gland. This review will focus on the structure, functions and mode of regulation of the prostate gland.

Up-regulation of androgen receptor binding in male rat fat pad adipose precursor cells exposed to testosterone: study in a whole cell assay system

Binding of androgens to adipocytes has previously been evaluated using cytosol fractions without taking into account nuclear binding, although the latter is suggested to be close to the physiological site of action. In the present study, performed in differentiated fat pad adipose precursor cells, we describe a simple, reliable and reproducible androgen binding assay in a system with intact cells. Tritiated and unlabeled methyltrienolone (R1881) were used to define specific and unspecific androgen binding. Triamcinolone acetonide was added to prevent the binding of R1881 to other types of receptors. Differentiated adipose precursor cells contain a homogeneous class of high affinity androgen binding sites, and binding is saturable and reversible. Binding apparently occurs at one site, with a Kd in the range of physiological androgen concentration (about 4 nM). Competition studies indicate that the receptor is specific for R1881, testosterone and dihydrotestosterone, which have approximately the same affinity, while progesterone, estradiol and dexamethasone show much lower affinity. Androgen binding was markedly enhanced after cellular exposure to R1881 and testosterone but not dihydrotestosterone, and this increase was dependent on protein synthesis, suggesting the formation of new receptors by these androgens. In conclusion, fully differentiated adipocytes contain a specific, high affinity receptor, the density of which is dependent on androgens.

Differential regulation of androgen receptors in the separate rat prostate lobes: androgen independent expression in the lateral lobe

In order to understand the hormonal regulation of androgen receptors (AR) in the separate lobes of the rat prostate gland, the present study examined AR levels in the ventral, dorsal and lateral prostate lobes as a function of androgen withdrawal to complete prostatic regression and subsequent testosterone replacement. In the intact rat, the 3 prostate lobes contained significantly different amounts of androgen binding sites. Mean number of total cellular AR in the ventral, dorsal and lateral lobes was 7370, 1690, and 1015 fm/mg DNA, respectively. These receptors were primarily localized within the nuclear fraction of homogenized tissue: ventral, 86%; dorsal, 83%; and lateral, 100% nuclear localization. Androgen withdrawal was initiated via castration and rats were sacrificed 1, 2, 3, 5, 7, 10 and 14 days thereafter. Nuclear AR levels fell rapidly to 5, 24 and 30% of intact values by 48 h in the ventral, dorsal and lateral lobes, respectively. Levels of nuclear AR continued to decline in the ventral and dorsal lobes to undetectable levels by Day 10. In marked contrast, lateral lobe nuclear AR began to increase on Day 3 postcastration, reaching intact values by Day 7 and 133% intact levels by Day 14. Cytosolic AR in the ventral and dorsal lobes initially increased following castration, but subsequently declined to low levels by Day 14. Cytosolic AR were not detectable in the lateral prostate at any time point following castration. To determine the nuclear AR response to testosterone at this time, 14 day castrate rats were given 2 cm testosterone implants and sacrificed 1, 3, 5, 7, 10 and 14 days thereafter. As expected, nuclear AR rapidly returned in the ventral and dorsal lobes by Day 1 and reached a plateau by Day 5. A short term response to androgen exposure occurred in the lateral lobe where an immediate 9-fold increase in nuclear AR quantity was observed; however, these levels rapidly declined to pre-implant values by Day 5 and remained at that level despite continued exposure to testosterone. These f findings indicate that while nuclear AR levels in the ventral and dorsal prostate are primarily regulated by androgens, a testosterone-independent component exists within the lateral lobe.

The equivocal presence of nuclear androgen binding proteins in mammalian spermatids and spermatozoa

The presence of nuclear androgen binding proteins measured by nuclear androgen exchange in rat spermatids and spermatozoa was re-examined. Specific binding was observed to be related to less dense contaminating particles when sonicated testes were fractionated by isopcynic centrifugation through a 40-61% Nycodenz linear gradient. No specific binding was observed in a pure preparation of epididymal spermatozoa collected by retrograde perfusion of the cauda epididymidis, even when a nuclear exchange assay of superior sensitivity was used. Contamination could easily be induced by adding prostatic tissue to epididymal spermatozoa prior to sonication. Despite this strong evidence that the measure of nuclear androgen receptors by nuclear exchange in germ cells is artefactual, the persistence of high endogenous concentrations of 5 alpha-dihydrotestosterone and 5 alpha-diols (but not testosterone) in spermatozoa of castrated rats argues for the opposite conclusion.

Influence of neonatal diethylstilbestrol treatment on androgen and estrogen receptor levels in the mouse anterior prostate, ventral prostate and seminal vesicle

Perinatal exposure to the synthetic estrogen, diethylstilbestrol (DES), affects the structure of both male and female reproductive systems. Changes may also occur in the levels of steroid hormone receptors. Cytosolic and nuclear androgen and estrogen receptor levels (expressed per mg DNA) from the sex accessory glands of male BALB/c mice exposed neonatally to DES were analyzed by exchange assays. Neonatal DES exposure caused significant decreases in: (1) cytosolic androgen and cytosolic and nuclear estrogen receptor levels in the anterior prostate and (2) cytosolic estrogen receptor levels in the ventral prostate. A significant increase was seen in the cytosolic estrogen receptor levels in the seminal vesicle. Significant decreases in cytosolic protein levels occurred in all DES-exposed glands.

Evidence for an androgen binding protein in the testis of a teleost fish (Salmo gairdneri R.): a potential marker of Sertoli cell function

A factor binding tritiated testosterone was detected using "steady-state" polyacrylamide-gel electrophoresis, in rainbow trout genital tract. It migrated with a Rf identical to that of rat ABP. This binding was thermolabile, and was competitively inhibited by unlabelled testosterone. The steroid binding protein was found in cytosols from trout testes which had been previously perfused to avoid blood contamination, trout seminal plasma and in testicular explants incubation media. Using a quantitative assay and a Scatchard analysis, 25-50 pmol binding sites per gram gonad were found in testis cytosol. Binding affinity constant for testosterone in the various samples was close to 4 x 10(8) M(-1). The dissociation of steroid-protein complex was rapid (t 1/2 approximately 1.5 min). Hormonal specificity was studied by the competition of 3H-T binding with several concentrations of unlabelled competitors and the following order for affinities was obtained: dihydrotestosterone approximately androstenedione greater than testosterone greater than oestradiol greater than 17 alpha, 20 beta DHP greater than 11KT greater than cyproterone acetate greater than cortisol. High testicular cytosol and seminal plasma concentrations and apparent in vitro production indicate that the testis may synthesize an ABP-like protein in the trout. Such a factor would provide a unique marker of Sertoli cell activity and regulation in various physiological or experimental situations.

Androgen receptor-deficient Tfm cells in the mosaic epididymis of sex-reversed mice heterozygous for Tfm: an autoradiographic study with [3H]-dihydrotestosterone and [3H]-estradiol

Testicular feminization (Tfm) in the mouse is characterized by androgen insensitivity of the target cells. We describe the presence of androgen-insensitive Tfm cells in the epididymis of mosaic mice produced by converting female carriers of the Tfm mutation (XTfm/X+) to males via the sex reversal factor (Sxr). The mosaic arises by random X-inactivation. In the epididymal duct, flat undifferentiated Tfm cells are interspersed between high columnar wild-type cells. By thaw-mount autoradiography we show that after injection of [3H]dihydrotestosterone, radioactivity is concentrated in the nuclei of high columnar wild-type cells, whereas the nuclei of the low cuboid Tfm cells remain free of nuclear radioactivity. After injection of [3H]estradiol, both Tfm and wild-type cells show nuclear labeling. Our observations demonstrate that Tfm cells in the mosaic epididymis selectively lack nuclear dihydrotestosterone-binding sites, whereas estradiol-binding sites are intact.

Prostate adenocarcinoma: effects of castration on in situ androgen uptake by individual cell types

The cellular distribution of androgen uptake was investigated in normal prostate and in Dunning R3327H prostate tumors in Copenhagen rats in vivo at different time intervals after castration. Quantitative dry-autoradiography was used to demonstrate which cell types have androgen binding, and to quantify the amount of androgen binding per cell type during initial castration-induced tumor regression and subsequent tumor relapse. Regardless of time after castration, tumor stromal nuclei had significantly more 3H-dihydrotestosterone (DHT) labelling than did tumor epithelial nuclei (p less than .001). On the other hand, prostate gland epithelial nuclei showed more 3H-DHT binding than prostate gland stromal nuclei. Tumor stromal nuclei had greater DHT uptake than any other cell type measured in the tumor or in secondary sex organs at all times after castration. Different cell types responded differently to castration. The 3H-DHT uptake measured in tumor stromal nuclei after castration showed that one day after castration 14.6 +/- 2.1 silver grains were present, 14 days after castration 9.3 +/- 2.4 were seen, and 50 days after castration 18.9 +/- 1.8 were present. This significant increase from 14 days to 50 days is not seen in the other cell types. This study gives insight into the cellular androgen receptor distribution in normal and malignant rat prostate tissue.

Testosterone regulation of androgen receptor levels in the uropygial gland of quails (Coturnix coturnix): a further proof for the androgen dependency of the uropygial gland

In castrated quails supplemented with testosterone by a chronically implanted silastic capsule, removal of the implant resulted in the gradual disappearance of the androgen receptors in both cloacal and uropygial glands. However, after a 7-day time span, the receptors reappeared in both glands but did not reach the original level of implanted birds. On the other hand, the photostimulation of intact birds induced an increase of the receptor content of their uropygial and cloacal glands when compared to sexually quiescent birds. These results show that, the concentration of the androgen receptors of the uropygial and cloacal glands of adult male quails is partly controlled by testosterone. By comparison with the mechanism of the action of testosterone in mammal target organs, our results add weight to the androgen dependency of quails uropygial glands (a sebaceous like organ).

Hydrophobic interaction chromatography (HIC) for the separation of protein-bound and free steroids. Application to binding protein and receptor assays

Protein-bound steroids can be separated from free steroids using microcolumns of silica gel coated with an hydrophobic (octadecyl) solid phase. The bound fraction is eluted in the assay buffer, whereas the free fraction is retained quantitatively on the column in the first step and can be recovered in methanol. Both fractions can be quantitated directly (e.g. by liquid scintillation spectrometry when using radioactive ligands) or kept for further analysis (e.g. by TLC, HPLC etc.). Separation of the bound and free fractions is rapid, accurate and reproducible; intra- and inter-assay coefficients of variation are lower than 5 and 10%, respectively. Recovery of radioactive steroids is high (usually over 85%) and can be estimated separately for each sample. Since assay blanks are very low (typically less than 0.1% of input), this new method, which could be termed "hydrophobic interaction chromatography" (HIC), should prove especially useful for the development of sensitive binding assays, particularly in the field of steroid receptors. The HIC method compared well with three methods currently used for steroid binding assays, namely adsorption of unbound steroids on dextran-coated charcoal, gel filtration on Sephadex LH-20 and adsorption of steroid-protein complexes on DEAE-cellulose filters. Examples of application described here include studies on human plasma sex hormone binding globulin (SHBG) and SP2 placental protein (saturation analysis, binding specificity etc.), the separation of antibody-bound steroids in a radioimmunoassay and the estimation of androgen binding to rat epididymal androgen binding protein (rABP). Receptor assays are illustrated by saturation analysis of the mouse uterine oestrogen receptor and of the androgen receptor in the human genital skin.

Augmentation of androgen-receptor binding in vitro: studies in normals and patients with androgen insensitivity

Using a simple whole-cell binding assay, the effect of androgens on receptor binding activity was studied in genital skin fibroblasts (GSF) from normals and patients with either androgen insensitivity syndrome (AIS), isolated micropenis or hypospadias. Expressing the response as a ratio of augmented to basal specific dihydrotestosterone (DHT) binding, there was a 2.4 +/- 0.87 (mean +/- SD) increase following 20 h incubation with 2 nmol/l [3H]-DHT in normal GSF. Mibolerone, a synthetic nonmetabolizable androgen, produced a similar response. Augmentation was temperature dependent, independent of androgen metabolism and suppressed by protein and RNA inhibitors. All patients with isolated micropenis and hypospadias demonstrated normal augmentation of receptor binding activity. There was no response in patients with complete AIS who were receptor negative. In the majority of patients with partial AIS, there was an in vitro response to androgens; those reared as males all virilized with androgen therapy. In contrast, a male patient with partial AIS who failed to respond to high-dose androgen therapy, showed no augmentation of specific androgen binding in GSF preincubated with androgens. This technique may be a useful in vitro bioassay to predict androgen responsiveness in vivo in patients with androgen insensitivity, either soon after birth in the short-term, or later at puberty.

Androgen receptor in genital tubercle of rabbit fetuses and newborns. Ontogeny and properties

In newborn rabbits of both sexes, an androgen receptor was characterized in the genital tubercle. Homogenates exhibited high affinity (Kd was about 0.4 nM) and saturable binding of [3H]methyltrienolone. The half-life of the [3H]5 alpha-dihydrotestosterone-androgen receptor complex was 72 h at 4 degrees C. The receptor was inactivated by heat and pronase and the binding was specific for potent androgens. Sucrose gradient analysis revealed a 8-9 S [3H]methyltrienolone binding protein in cytosols from both sexes. Androgen binding, in the homogenate, was detected as soon as day 18 of gestation in both sexes and the number of binding sites increased until birth. During sexual organogenesis and at birth there were no major differences between males and females in the amount or affinity of androgen binding. Specific androgen binding was also detected in sexual ducts of male and female newborns.

A new exchange procedure for the quantitation of prostatic androgen receptor complexes formed in vivo

A procedure is described for the measurement of rat prostatic androgen receptor saturated in vivo with non-radioactive androgen. While NaSCN alone induces irreversible dissociation (denaturation) of androgen from the receptor, the combination of this chaotropic salt (0.15 M) with sucrose (15%) and sodium molybdate (10 mM) allows the exchange of R DHT with [3H]DHT at 0 degrees C with only minimal receptor denaturation. The validity of the present exchange assay is based on the following: a similar quantity of androgen receptor was detected when binding was measured directly after in vivo treatment with radioactive androgen or indirectly by [3H]DHT exchange after treatment with non-radioactive androgen. Steroid specificity, sedimentation analysis and equilibrium association constants indicated that this exchange assay labels the androgen receptor without interference from other prostatic steroid binding proteins. With this method it is now possible to quantitate not only prostatic androgen receptors bound to androgens in vitro but also hormone-receptor complexes formed in intact animals under the influence of endogenous androgen.

Differential distribution of 3H dihydrotestosterone and 3H estradiol nuclear binding sites in mouse male accessory sex organs. An autoradiographic study

The distribution of specific nuclear binding sites for androgens and estrogens in the male accessory sex organs of the mouse was assessed by autoradiography with 3H dihydrotestosterone (3H DHT) and 3H estradiol (3H E2). With 3H DHT nuclear labeling differed among the epithelia of the organs. It was high in seminal vesicle and ampullary gland, moderate in ventral prostate, urethral gland, prostatic excretory ducts and the ampulla ductus deferentis, low in dorsal prostate and low or absent in coagulation gland. With 3H E2, in contrast, epithelial nuclear labeling was high only in coagulation gland, moderate or low in seminal vesicle, low or absent in ventral and dorsal prostate and absent in ampullary gland and ampulla ductus deferentis. In the lamina propria of all organs nuclear labeling with 3H DHT was generally moderate and existed only in some cells, with the highest number in the ampulla ductus deferentis. With 3H E2, nuclear labeling in the lamina propria showed a high intensity in all organs, except in ventral and dorsal prostate which remained unlabeled. Many labeled cells were found in the deferent duct and its ampulla, while in the other organs only a few cells showed nuclear labeling with 3H E2. In the smooth muscle sheath of all organs, some muscle cells were moderately labeled with 3H DHT, but not with 3H E2. The results indicate the presence of nuclear receptors in male accessory sex organs for both dihydrotestosterone and estradiol. The differential patterns of 3H DHT and 3H E2 nuclear uptake suggest differential sensitivities of the individual organs and their tissue compartments for androgens and estrogens.

Sex steroid receptors in normal and hyperplastic human prostate

The concentrations of sex steroid receptors (per unit DNA) were measured in normal periurethral and peripheral prostatic tissue samples from seven men (mean age 64 years; range 54-71 years) undergoing cystectomy for bladder cancer, and in hyperplastic nodules from 15 men with BPH (mean age 69 years; range 60-89). Occupied androgen (AR) and estrogen (ER) receptors were measured with an improved exchange procedure, where receptor-binding sites were stabilized by a combinatorial procedure involving careful washout of extracellular secretory products (including proteases) prior to homogenization, inclusion of 0.5 mM phenylmethyl sulfonylfluoride (PMSF) and 20 mM molybdate in the exchange medium, and long-term incubation at 0-4 degrees C. Bound radioligands were separated by a hydroxylapatite (HAP) batch adsorption procedure. Maximal specific exchange binding of 3H-R 1881 or 3H-estradiol in total homogenates of human prostate samples was achieved after incubation periods of about 72 h at 0-4 degrees C. In contrast, progestin receptors (PR) were readily available for binding 3H-R 5020; thus overnight binding at 0-4 degrees C was routinely used to measure PR. Binding specificities and equilibrium binding constants (calculated from 8-point Scatchard plots, correcting for nonsaturable binding) were found to be characteristic for AR, PR, and ER, respectively. The receptor results obtained in this study demonstrate that no significant differences existed in total AR per unit DNA between hyperplastic and either central or peripheral prostatic tissue samples; PR was present in both zones of normal prostatic tissue as often as in BPH samples, with PR concentrations significantly lower in hyperplastic samples; and ER was irregularly detected in both normal and hyperplastic tissue in low concentration relative to AR and PR; the frequency of ER detection was much lower in BPH than in normal prostate tissue. Studies of steroid receptor content relative to enzyme markers specific for epithelial and stromal cells in BPH samples showed a positive correlation between acid phosphatase activity (a specific marker for epithelial cells) and both AR and PR. No correlation was observed between AR or PR with either prolyl hydroxylase or myosin ATPase (specific markers for stromal cells). These observations suggest that PR, as well as AR, is primarily associated with the epithelial elements of prostate. Because of the relative infrequency of ER, similar correlation of ER with enzyme markers was not possible.

In vitro age-dependent incorporation of [1-14C]acetate into lipid subclasses in rat ventral prostate

The [1-14C]acetate incorporation into different lipid subclasses by the rat prostate gland was lineal between 20 and 80 mg of wet tissue. The in vitro [1-14C]acetate incorporation into lipid subclasses was a development-dependent process. The highest values of [1-14C]acetate incorporation into triacylglycerols, free cholesterol and esterified cholesterol were observed at puberty, but radioactivity incorporation into phospholipids was similar in both prepuberty and puberty, then decreasing in maturity. The relationship between triacylglycerols, free cholesterol and esterified cholesterol with respect to total lipids was about 12, 10 and 3.5%, respectively, values being maintained during the animal development. The in vitro [1-14C]acetate incorporation into lipid subclasses in castrated rats decreased considerably as compared with normal rats.

Characteristics of separated epithelial and stromal subfractions of prostate: I. Rat ventral prostate

These studies were initiated with the objective of isolating epithelial and stromal cells of human prostatic tissue in undamaged state, in order to study the cellular distribution of steroid receptors in benign prostatic hyperplasia (BPH) relative to normal prostate. Initial experiments showed that when BPH tissue immersed in tissue culture media was progressively fragmented by various cutting procedures, epithelial elements were selectively released as clumps of variable size and individual cells, but that a large percentage of these cells were damaged, as evidenced by their failure to exclude trypan blue (TB). These observations suggested that if tissue fragmentation were carried out under defined conditions that minimize cell damage, BPH subfractions might be obtained containing a large percentage of undamaged cells. To determine conditions of tissue fragmentation which result in maximal recovery of epithelial cells which exclude TB, rat ventral prostate (RVP) was chosen as a model system. Experiments with RVP revealed that maximal yields of such cells were obtained in "large" epithelial clumps (greater than 30 cells per clump) released under the following conditions: (1) chopping the tissue with razor blades in a large volume (2 ml/100 mg RVP) of a Ca2+-free tissue culture medium ( Joklik 's-MEM) containing 1% casein, (2) carrying out the entire fractionation procedure in the cold, and (3) maintaining a 1% casein concentration in the medium during chopping, as well as in subsequent washing procedures, to protect cells from proteolytic activity. In large epithelial clumps, cells in the interior of the clump were not stained by TB but the cells at the periphery of the clump were freely permeable to TB. Single epithelial cells and small epithelial clumps (3-10 cells) released by razor blade fragmentation were also permeable to TB. When large epithelial clumps were incubated at 20 degrees C for 90 min, the clumps disaggregated into smaller clumps and morphologically intact single cells, which did not exclude TB. The residual tissue fragments remaining after chopping contained the bulk of stromal cells plus some epithelial elements. The latter could be removed by gentle rubbing of the fragments on a sieve in the presence of medium. The stromal fraction thus obtained consisted of stromal cells, embedded in mesenchymal matrix, which were not stained by TB and appeared normal when examined histologically by light microscopy.(ABSTRACT TRUNCATED AT 400 WORDS)

Differential distribution of dihydrotestosterone and estradiol binding sites in the epididymis of the mouse. An autoradiographic study

The distribution of androgen and estrogen binding sites in the mouse epididymis was assessed by autoradiography with 3H dihydrotestosterone (3H DHT) and 3H estradiol (3H E2). Nuclear labeling with 3H DHT in principal cells of the epithelium is high in the caput, low in the corpus, and high again in the cauda. 3H E2 also binds to the nuclei of principal cells. The pattern is distinct from 3H DHT: nuclear labeling is highest in the ductulus efferens and high in the caput, but low or absent in corpus and cauda. Apical cells in caput and clear cells in corpus and cauda are moderately labeled with 3H DHT but heavily labeled with 3H E2. Connective tissue cells show variable labeling with both hormones, being more pronounced with 3H E2. Smooth muscle cells are also labeled to varying degrees with both hormones. The different binding patterns of 3H DHT and 3H E2 and the results of the competition studies with unlabeled compounds demonstrate that in the epididymis besides the specific nuclear receptors for androgen also estrogen receptors are present.

Regulation and compartmentalization of androgens in rat prostate and muscle

Male rats were castrated and treated with various doses of testosterone (T) or 5 alpha-dihydrotestosterone (DHT) by implantation of steroid releasing polydimethylsiloxane depots. After 14 days, the animals were killed and the concentration of T, DHT and 5 alpha-androstane-3 alpha,17 beta-diol (Diol) was measured by radioimmunoassay in plasma, in the homogenates of the prostate (PR), the bulbocavernosus/levator ani muscle (BCLA), skeletal muscle (SM) and heart muscle (HM), as well as in the cytosol and the nuclear fraction of these tissues. Additionally, the weight and DNA content of PR and the levator ani muscle were measured. The main results were: After T or DHT administration the main androgens in plasma were T or Diol, respectively, the concentration of each being linearly dependent from the administered steroid dose (T after T-: r = 0.97, P less than 0.001. Diol after DHT administration: r = 0.97, P less than 0.001). T in a dose of 60 micrograms/24 h maintained the concentrations of T, DHT and Diol in plasma in the range of untreated controls. Irrespective of the T doses administered, its concentration in PR tissue was comparatively low. T administration resulted in a significant accumulation of DHT in PR, when compared to plasma T. The steepest increase of DHT in PR was found with low doses of T administered (0.6-12 micrograms/24 h). At higher doses (12-600 micrograms/24 h) the further increase in the tissue was rather parallel to that of plasma T. A comparable picture was found for the DHT concentration in cytosol and in nuclei. The Diol concentration in the cytosol was linearly related to the administered T dose (r = 0.80, P less than 0.001). This steroid could not be detected in nuclei (less than 0.5 pmol/mg DNA). Administration of DHT in principle mimicked the DHT data observed after T treatment. In muscle homogenates no accumulation of neither T, DHT nor Diol was observed. In the nuclear fractions only after the highest doses of T measurable amounts of T and DHT were found. Whereas a positive correlation between DHT values in nuclei and weight increases in prostate was present, no such parallelism could be demonstrated in muscular tissue. The data are discussed with respect to the present knowledge of androgen binding and metabolism in different organs and to a possible specific role of nuclear DHT accumulation in mediating androgen dependent processes.

Characterization of steroid binding specificity of the androgen receptor in human foreskin fibroblasts

Our objective was to evaluate a convenient in vitro model for measuring steroid affinities to the human androgen receptor. The ability of unlabeled analogues of dihydrotestosterone (DHT) to compete with [3H]DHT for binding to the receptor in human fibroblasts was measured and expressed relative to DHT. The C-3 ketone group and the planar configuration of the A and B rings were critical for binding. Absence of the 10 beta-methyl group increased affinity of the androstane compounds for the receptor. The 17 beta-hydroxyl group was also essential for high affinity binding and addition of a 17 alpha-methyl group enhanced binding. Binding of steroids with a delta 4 double bond was consistently less than that of the 5 alpha-reduced steroids. This was true of both the androstene and estrene series. We conclude that human foreskin fibroblasts offer a useful model for in vitro studies characterizing the effects of steroid structural modifications on binding to the human androgen receptor.

Nuclear testosterone receptors in the ovine testis

Nuclear [3H] testosterone-receptor complexes were demonstrated in hypophysectomized ram testis after in vitro direct labelling. The nuclear binding was maximal after a 45 min incubation of the tissue. The receptors are extractable by 0.4 M KC1 or NaSCN with a 25-30% efficiency. They migrate towards the anodic region during electrophoresis on agar gel. Nuclear androgen receptors were characterized in intact lamb testis by a testosterone exchange assay. After precipitation by protamine sulphate, the receptors were labelled with [3H]testosterone during a 12 h incubation at 4 degrees C. The exchange activity was linear between 0.1 and 0.9 mg of DNA per ml of incubation buffer. The receptors bind testosterone with a limited capacity (40-180 fmoles per mg DNA) and a dissociation constant Kd of 2 x 10(-9) M. Their relative affinities for steroids are dihydrotestosterone greater than testosterone greater than estradiol greater than progesterone greater than 5 alpha-androstanediol greater than cyproterone acute greater than R5020.

Assay and characterization of ovarian testosterone receptor

Ovarian cytosol from immature, hypophysectomized rats was used to characterize the biochemical properties of ovarian androgen receptor and to develop a reliable and convenient assay procedure for its measurement in small quantities of tissue. The results show that Sephadex G-25 columns provide a rapid and reliable method to separate bound from free testosterone for assay of androgen receptor in the ovarian tissue. The binding affinity (KD = 0.6 nM) and sedimentation value (8S) for the ovarian androgen receptor are similar to other steroid receptors and is saturable. It is inactivated by heat and protease digestion and the binding is specific for potent androgens. The ovary contains approximately equal quantities of androgen and estrogen receptor. A physiological role for the presence of androgen receptor in the ovarian tissue is proposed.

Induction of androgen receptor formation by epithelium-mesenchyme interaction in embryonic mouse mammary gland

The role of tissue interaction in the development of hormone responsiveness was studied in the embryonic mammary gland of the mouse, which becomes sensitive to testosterone on day 14. Previously, the mesenchyme had been identified as the sole target tissue for the hormone, although it was also demonstrated that its response to testosterone required the presence of mammary epithelium. Using autoradiography, we now show that [3H]testosterone or [3H]5 alpha-dihydrotestosterone is bound only by those mesenchymal cells closest to the epithelial mammary bud. When mammary epithelia were experimentally associated with mesenchyme of the mammary region and cultured together for 3 days in vitro, they also became surrounded by several layers of [3H]testosterone-binding mesenchymal cells. Correspondingly, this tissue association was accompanied by a substantial increase of androgen-binding sites in the explants. No hormone-building mesenchymal cells were seen in combinations with epidermis or pancreas epithelium; only salivary epithelium showed a weak positive effect. From these results we conclude that mammary epithelium induces the formation of androgen receptors in adjacent mesenchyme and thereby controls the development of androgen responsiveness in this tissue.

Acute therapy with megestrol acetate decreases nuclear and cytosol androgen receptors in human BPH tissue

This study measures the effect of megestrol acetate (Megace), a progestational antiandrogen, on nuclear and cytosol receptor concentrations in human BPH prostates. Prostatic tissue was obtained at surgery from both untreated patients with BPH and patients pretreated for three to eleven days with 120 to 160 mg of Megace daily; tissues were homogenized and separated into cytosol and crude nuclear fractions. Cytosol and salt extractable nuclear fractions were subjected to saturation analysis with 3H R1881 over the range of 0.5 to 10 nmoles in exchange reactions for 20 hours at 15 degrees C. Cytosol receptor concentration decreased significantly from 32.7 to 8.7 femtomoles per mg protein (P less than 0.05); nuclear receptor also was significantly reduced from 317 to 43.8 femtomoles (fmole) per mg DNA (P less than .001). Plasma testosterone also decreased significantly from 3.65 to 1.01 ng/ml in Megace-treated patients. These effects of Megace on receptor concentration appear to be qualitatively quite different from those reported following castration in animals or following high-dose estrogen therapy in humans. The mechanism of action of Megace in decreasing both cytosol and nuclear androgen receptor concentrations is unknown. It is possible that decrease in receptor concentration is secondary to either the progestational or antiandrogenic effects of Megace. These possibilities are currently under study.

Androgen receptors in the diabetic rat

Male rats rendered diabetic by IV streptozotocin (65 mg/kg body weight) were treated with exogenous insulin or testosterone. Charcoal-coated dextran and polyacrylemide gel electrophoresis techniques were employed in studying the characteristics of androgen (R1881) binding to prostate cytosol protein. In comparison with normal (N) rats, the replacement therapy of diabetic (D) animals with insulin (D + I) or testosterone (D + T) was able to restore epididymal weight (N = 0.40 +/- 0.04 g; D = 0.18 +/0 0.02 g; D + I = 0.42 +/- 0.05 g; D + T = 0.40 +/0 0.06 g) and total prostate weight (N = 0.24 +/- 0.02 g; D = 0.15 +/- 0.02 g; D + I = 0.24 +/- 0.05 g; D + T = 0.35 +/- 0.06 h). Testicular endogenous content of testosterone was restored after insulin treatment (N = 154 +/- 13 ng/testis; D = 41 +/- 5 ng/testis; D + I = 142 +/- 9 ng/testis), and significant improvements of serum testosterone levels were also achieved (N = 540 +/- 64 ng/100 ml; D = 238 +/- 37 ng/100 ml; D + I = 358 +/- 18 ng/100 ml). Prostate cytosol of streptozotocin-diabetic rats had strongly lowered capacity for 3H-R1881 binding compared with controls (94 and 12 fmol/mg protein, respectively). Testosterone treatment produced a 3.3-fold improvement of this lowered value, whereas the increment seen with insulin was less (1.5-fold). It is emphasized that some of the improvements caused by insulin replacement therapy in diabetic animals are due to the partial restoration of testosterone secretion. Thus, the combined actions of insulin and testosterone (instead of insulin alone) seem to be of major importance in the maintenance and regulation of accessory sex glands function.

The effect of therapy on the concentration and occupancy of androgen receptors in human prostatic cytosol

With a protamine sulphate precipitation method, total and free cytosol AR was assayed in BPH and prostatic carcinoma tissue, in order to investigate possible differences in AR concentration that might relate to the histo-pathology of the tissue or to endocrine manipulation of the patients. Similar ranges of total cytosol AR concentrations were observed in BPH and untreated prostatic carcinoma, but the latter tended to have a higher proportion of apparently free sites. Moreover, the proportion of "free" sites in the untreated carcinoma tissue appeared to be related to the proportion of poorly differentiated carcinoma in the specimen. In patients whose endogenous androgen levels had been lowered by treatment, the proportion of free sites tended to be higher, but a considerable proportion of sites appeared to be still occupied. Carcinoma tissue from some estrogen-treated patients had high cytosol AR concentrations. It is suggested that, in some treated patients, androgens of adrenal origin may occupy some AR sites and that some carcinomas may contain a considerable concentration of nonfunctional AR.

Androgen binding in the baboon prostate

Androgen receptors were identified and partly characterized in cytosols of the caudal and cranial prostatic lobes of a 24-hr castrate baboon. Binding of cyproterone acetate (CA) to testosterone-binding globulin (TeBG) in baboon serum was negligible and therefore was an appropriate unlabeled competitor for distinguishing high-affinity binding of tritiated dihydrotestosterone (3H-DHT) to serum contaminants and receptors in cytosol preparations when multiple-point saturation analyses and removal of free steroid by charcoal adsorption were used. Specificity of androgen binding was demonstrated by the inability of diethylstilbestrol, a synthetic estrogen known to have low binding affinity for TeBG, to displace 3H-DHT from the receptor protein. The number of high-affinity binding sites and the dissociation constant of the androgen receptor calculated for the caudal lobe were 102 fmoles/mg cytosol protein and 4.0 X 10(-9) M, respectively; corresponding values for the cranial lobe were 49 fmoles and 1.3 X 10(-9) M.

Mechanisms of replenishment of nuclear androgen receptor in rat ventral prostate

1. The concentration of androgen receptor in the nucleus of the prostatic cell is rapidly elevated by the administration in vivo of 2mug of [(3)H]testosterone to 1-day-castrated rats. From a concentration of 2300 receptors/nucleus at 5min after intravenous injection of hormone, there is an increase to 21000 receptors/nucleus at 60min. At the same time, the amount of binding of androgen in the cytoplasm remains constant at a relatively low value. 2. An identical dose of [(3)H]testosterone administered to 7-day-castrated rats produces a much smaller change in the concentration of nuclear receptor, from 700 receptors/nucleus at 5min to only 4300 receptors/nucleus at 60min. Thus the reservoir from which nuclear receptor is replenished is considerably smaller in regressed prostatic cells. Again, the amount of binding of androgen in the cytoplasm remains unchanged at a low value over the experimental time course of 60min. 3. In contrast with the scant labelling of cytoplasmic receptor achieved by injecting animals with [(3)H]testosterone, labelling in vitro, by incubation of tissue slices with radioisotope, indicates that prostate of 1-day-castrated animals actually contains 21400 receptors/cell in the cytoplasmic compartment, and prostate of 7-day-castrated animals 3000 receptors/cell. 4. Owing to the similarity between the concentration of nuclear receptor measured in vivo and the concentration of cytoplasmic receptor measured in vitro, the labelling techniques in vivo and in vitro were used in sequence to demonstrate the movement of most of the cytoplasmic receptor into the nucleus. In the 5-60min interval after the administration of [(3)H]testosterone to 1-day-castrated rats, a decrease of 17400 receptor molecules in the cytoplasm is exactly mirrored by an increase of 17200 receptor molecules in the nucleus. 5. These results imply that, in prostate of 1-day-castrated rats, nuclear receptor is replenished exclusively by translocation of cytoplasmic receptor. However, in the regressed prostate of 7-day-castrated rats, only about 25% of the nuclear receptor is replenished through translocation of existing cytoplasmic receptor. The remainder is ultimately synthesized during new rounds of cell division induced by hormone.

Prostatic binding protein. A steriod-binding protein secreted by rat prostate

Rat prostatic cytosol contains a high concentration of a prostatic binding protein with peculiar steroid-binding properties. Indeed, in spite of a relatively low affinity, charcoal adsorption can be used for its measurement. Furthermore, the binding is not specific for particular steroids and increases very strongly after delipidation. In delipidated cytosol the concentration of the binding site is 3.1 micronmol/g protein and the apparent affinity for pregenolone 1.7 X 10(6) M-1. The high concentration of prostatic binding protein in prostatic fluid shows that this substance is secreted by the prostate. Prostatic binding protein has the following physicochemical characteristics: it is precipitated by ammonium sulfate between 50 and 70% saturation; the elution position from a Sephadex G-100 column corresponds to a molecular weight of 51000; it sediments in sucrose density gradients at 3.7 S and is eluted from DEAE-cellulose columns at about 0.25 M KCl. On polyacrylamide gel electrophoresis the binding activity coincides with the major cytosolic protein band. This band has the same mobility as serum albumin in 7% gels, but a higher mobility in more concentrated gels.