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At least 487 records · Page 27Linked to original sources
PubMed1981

Binding of methyltrienolone to glucocorticoid receptors in rat muscle cytosol.

Androgen receptor measurements with [3H]-methyltrienolone [17 beta-hydroxy-17 alpha-methyl-estra-4,9,11-trien-3-one (R1881)] or [3H]testosterone in vastus lateralis muscle cytosol of intact male rats yielded similar numbers of binding sites. Gonadectomy significantly increased the androgen receptor values, and both steroids gave similar results. The binding of [3H]-testosterone was not affected by adrenalectomy. In contrast, [3H]R1881 binding increased 2-fold after adrenalectomy. Competition experiments as well as sucrose density gradient analysis indicated that R1881, in addition to its binding of the androgen receptor, was also bound to glucocorticoid receptor. These results show that the synthetic androgen R1881 must be used with caution in tissues suspected to contain glucocorticoid receptors.

Adrenalectomy↗
PubMed1983

Ontogeny of mesenchymal androgen receptors in the embryonic mouse mammary gland.

We demonstrate the presence of a high affinity androgen-binding site in the embryonic mouse mammary gland, and describe its appearance and development from the initial formation of the gland bud (day 12) through the androgen-responsive stage (day 14) until term (day 19). Binding assays were done on entire organ rudiments exposed to the ligand [( 3H] testosterone, [3H]5 alpha-dihydrotestosterone, or [3H]methyltrienolone) in vitro, and receptor levels are expressed per gland. In competition experiments, the binding site shows a ligand specificity of a typical rodent androgen receptor. Scatchard analysis yielded a figure of 90-100 million binding sites for one 14-day gland, or approximately 30,000 per target cell. The apparent dissociation constant Kd for ligand binding by the intact tissue was between 0.55 and 0.75 X 10(-9) M. The first binding sites become detectable at the time of mammary bud formation (day 12); their number increases about 20-fold towards the responsive stage (day 14), and they persist at high levels at least until birth. The loss of androgen responsiveness on day 15 is neither accompanied by a loss of receptors nor by a change of their binding affinity.

Animals↗
PubMed1984

Control of androgen cytosol receptor concentrations in Sertoli cells: effect of androgens.

Androgen receptor concentrations were measured in Sertoli cells under a variety of conditions. After brief (30- to 60-min) incubation of cultured cells with [3H]R1881 (methyltrienolone), cytosol receptor concentrations were greatly diminished, and nuclear bound steroid was elevated. Removal of the exogenous steroid was accompanied by a return of cytosol receptor to preincubation concentrations by 1 h and a slower decline in nuclear bound steroid. In the continued presence of R1881 or testosterone, cytoplasmic receptor concentrations declined and then returned to or above preincubation concentrations by 6-17 h. Actinomycin-D and cycloheximide did not alter this pattern. Over this same interval, nuclear bound steroid concentrations remained elevated. Exposure of the cells to R1881 or testosterone for the entire 72-h culture period did not alter cytoplasmic receptor concentrations. Cytoplasmic androgen receptor concentrations were decreased in Sertoli cells from hypophysectomized rats 15-22 days after surgery compared to those in cells from intact controls. Treatment with testosterone propionate (0.5 mg/day) or FSH (75 micrograms/day) prevented the decline in receptor concentrations. Cryptorchidy (33 days) also decreased cytosol receptor concentrations. These data indicate that exposure to androgens can influence Sertoli cell cytosol androgen receptor concentrations in vitro and in vivo. The Sertoli cell adapts to the continual presence of androgens with a return of cytosol receptor while maintaining elevated concentrations of nuclear bound steroid. In vivo, androgen treatment can maintain cytoplasmic receptor concentrations in the absence of pituitary hormones in the immature rat.

Animals↗
PubMed1985

Species differences in prostatic steroid 5 alpha-reductases of rat, dog, and human.

The conversion of testosterone to 5 alpha-dihydrotestosterone by prostate particulates from rats, dogs, and humans was investigated, and significant species differences were found with their pH profiles, affinities for 4-azasteroidal inhibitors, and sensitivities to mercuric sulfhydryl reagents. The pH optima for the rat (pH 7), the dog (pH 6), and the human (pH 5) enzyme are significantly different. Mersalyl acid and p-hydroxymercuribenzoate inactivate only the rat 5 alpha-reductase, but not the human or dog enzyme. The rank orders of potencies of 24 3-oxo-4-azasteroids to inhibit 5 alpha-reductases of the rat, dog, and human prostate are different. The variation of the 17 beta-functional groups of the inhibitors demonstrates clearly the species differences. Those inhibitors with a 17 beta-diethylcarbamoyl, 17 beta-diisopropylcarbamoyl, 17 beta-t-butylcarbamoyl, or 17 beta-secbutylcarbonyl functional group are approximately equipotent as inhibitors of the rat and human enzymes, whereas they are only 0.1-15% as potent as inhibitors of the dog enzyme. On the other hand, those inhibitors with a 17 beta-spiroether functional group are most potent as inhibitors of the rat enzyme, are 15-50% as potent as inhibitors of the dog enzyme, and are 0.2-0.4% as potent as inhibitors of the human enzyme. Those inhibitors with a 17 beta-n-octylcarbamoyl, 17 beta-(1-carboxyethyl), or 17 beta-(1-carboxy-3-butyl) functional group are 2-3 orders of magnitude less potent as inhibitors of the dog and human enzymes than as inhibitors of the rat enzyme. These results suggest that prostatic 5 alpha-reductases of rats, dogs, and humans are significantly different. In spite of the significant species differences in inhibitor affinities, where determined, inhibition of the rat, dog and human enzymes by these compounds is competitive with testosterone. These 3-oxo-4-azasteroids have a similar rank order of potency as inhibitors of 5 alpha-reductase in human normal, benign hyperplastic, and cancerous prostates, indicating that the inhibitor-binding sites of 5 alpha-reductase in the prostate in different pathological states are similar. The affinities of the 3-oxo-4-azasteroids for rat prostatic cytosol receptor were determined. Five of these 5 alpha-reductase inhibitors have no significant affinity for the androgen receptor, whereas others do have an affinity for the receptor.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1989

Relative binding properties of microsomal and cytosolic androgen receptor species of the ventral prostate.

A comparison between a microsomal and a cytosolic source of receptor-like androgen-binding activity was made in the rat ventral prostate. Microsomal binders remain in solution at 90% saturation with (NH4)2SO4 and display equal affinity for 5 alpha-dihydrotestosterone (DHT) and mibolerone. They have a half-life of dissociation of steroid-receptor complexes of 96 +/- 11 h and a 5S sedimentation coefficient for the untransformed moiety, with the appearance of a 3.5S species after incubation at 24 C for 30 min. They do not acquire DNA-binding capability after heat- or salt-attempted activation. Cytosol binders precipitate upon 90% saturation with (NH4)SO4 and have higher affinity for DHT than mibolerone. The half-life for dissociation of complexes is 85 +/- 14 h, and the complex sediments as an 8S moiety which is able to transform to a 4.4S form after heat activation correlated with increased DNA-binding ability of these species. Unactivated cytosol steroid-receptor complexes are also able to bind to DNA in the presence of molybdate. Salt-induced activation of cytosol moieties only occurred in the absence of molybdate. Microsomal androgen receptor is more stable than cytosol androgen receptor independently of the presence of hormone or partial purification of the moieties; the inactivation rates of the two forms of complexes differ 3-fold. Results indicate that androgen-binding sites associated with the microsomal and cytosolic fractions of the prostate are distinct entities.

Animals↗
PubMed1990

The proliferative effect of "anti-androgens" on the androgen-sensitive human prostate tumor cell line LNCaP.

The effect of steroidal and nonsteroidal "anti-androgens" on the proliferative capacity of androgen-sensitive LNCaP-FGC human prostate tumor cells in culture was studied using charcoal-dextran stripped human serum-supplemented media. Cyproterone and medroxyprogesterone acetates, flutamide, hydroxyflutamide, and anandron (R23908) were administered alone at concentrations between 3 X 10(-12) and 3 X 10(-6) M. Results indicated that although medroxyprogesterone induced maximal proliferation at 3 X 10(-9) M, the other "anti-androgens" (with the exception of flutamide that was ineffective) were effective at 3 X 10(-8) M and higher concentrations; the amplitude of the proliferative response by these compounds was comparable to that elicited by estradiol-17 beta (3 to 5-fold over control). None of the anti-androgens tested triggered the shutoff effect characteristic of androgen action. When 3 X 10(-10) M DHT and the above mentioned anti-androgens were administered simultaneously, a synergistic pattern was seen; on the contrary, 3 X 10(-8) M DHT cancelled the proliferative effect of each of the anti-androgens when administered simultaneously. The relative binding affinity of these anti-androgens to androgen receptors present in LNCaP-FGC cells did not correlate well with their proliferative efficiency. The data collected were interpreted within the premises of the negative control hypotheses for the regulation of cell proliferation in metazoans. Within those premises, results became compatible with the notion that first, "anti-androgens" elicited the proliferation of androgen-sensitive cells by neutralizing the effect of a serum-borne inhibitor (androcolyone-I); this event seems not to be mediated by androgens receptors. Second, anti-androgens did not trigger a proliferative shutoff response like androgens do, i.e. the proliferative pattern induced by anti-androgens was comparable to that elicited by estrogens and progestins. Third, when administered simultaneously with 3 X 10(-10) M DHT, anti-androgens behaved synergistically. Fourth, the DHT-induced shutoff effect consistently overrode the proliferative effect generated by anti-androgens and estrogens when added alone. Finally, taken together these results raise important questions regarding the therapeutic role of anti-androgens in prostate cancer.

Androgens↗
PubMed1991

Multiple mechanisms for regulation of 3 beta-hydroxysteroid dehydrogenase/delta 5----delta 4-isomerase, 17 alpha-hydroxylase/C17-20 lyase cytochrome P450, and cholesterol side-chain cleavage cytochrome P450 messenger ribonucleic acid levels in primary cultures of mouse Leydig cells.

The regulation of mRNA levels for delta 5-3 beta-hydroxysteroid dehydrogenase/delta 5----delta 4-isomerase (3 beta HSD), 17 alpha-hydroxylase/C17-20 lyase cytochrome P450 (P450(17 alpha] and cholesterol side-chain cleavage cytochrome P450 (P450scc) was studied in primary cultures of mouse Leydig cells. Treatment of Leydig cells with 8-bromo-cAMP (cAMP) was essential for expression of P450(17 alpha) mRNA, but not for 3 beta HSD. Treatment with cAMP caused a decrease in basal levels of 3 beta HSD mRNA. The addition of aminoglutethimide (AG), an inhibitor of cholesterol metabolism, to the cAMP-treated cultures resulted in increased expression of both 3 beta HSD and P450(17 alpha) mRNA levels. The addition of testosterone or the androgen agonist mibolerone to cAMP- plus AG-treated cultures reduced 3 beta HSD and P450(17 alpha) mRNA to levels comparable to those observed when cells were treated with cAMP only. The glucocorticoid dexamethasone reduced both basal and cAMP- plus AG-induced increases in 3 beta HSD mRNA, but not in P450(17 alpha) mRNA. Estradiol at a concentration of 1 microM had no effect on cAMP- plus AG-induced 3 beta HSD or P450(17 alpha) mRNA levels. The role of protein synthesis in mediating the cAMP induction of 3 beta HSD, P450(17 alpha), and P450scc was investigated. The addition of cycloheximide (10 micrograms/ml) to cAMP-treated cultures for 24 h completely suppressed both constitutive and cAMP-induced 3 beta HSD mRNA levels. Cycloheximide also repressed cAMP-induced levels of P450(17 alpha) to 12% of levels observed in the absence of cycloheximide. In sharp contrast, 24-h treatment with cycloheximide did not suppress cAMP induction of P450scc mRNA, but reduced basal levels by approximately 50%. A time course of induction by cAMP (50 microM) of P450(17 alpha) and P450scc mRNA showed very similar rates of increase in P450(17 alpha) and P450scc mRNA, with the greatest increase occurring between 12 and 24 h of treatment. The results of the study demonstrate that in normal mouse Leydig cells steady state levels of mRNA for 3 beta HSD, P450(17 alpha), and P450scc are differentially regulated. cAMP is required for maximal levels of all three mRNAs. There is high constitutive expression of 3 beta HSD and P450scc mRNA, while expression of P450(17 alpha) mRNA is absolutely dependent on cAMP stimulation. Endogenously produced testosterone negatively regulates the expression of cAMP-induced P450(17 alpha) and 3 beta HSD, while the glucocorticoid dexamethasone negatively regulates 3 beta HSD and P450scc.(ABSTRACT TRUNCATED AT 400 WORDS)

3-Hydroxysteroid Dehydrogenases↗
PubMed1992

The biological activity of 7 alpha-methyl-19-nortestosterone is not amplified in male reproductive tract as is that of testosterone.

Based on the premise that testosterone, but not 7 alpha-methyl-androgens, is reduced at the 5 alpha-position in the prostate and seminal vesicles, the differential bioactivities of these androgens were investigated in castrated rats. The ability of 7 alpha-methyl-19-nortestosterone acetate (MENT) to increase the weights of ventral prostate and seminal vesicles of castrated rats was four times higher than that of testosterone, while its effect on the weights of bulbocavernosus plus levator ani muscles (muscle), was 10 times that of testosterone. MENT was also approximately 12 times more potent than testosterone in the suppression of serum gonadotropin levels. A dose of testosterone that maintains serum gonadotropin levels and muscle mass also maintains prostate and seminal vesicle weights in castrated rats. By contrast, a dose of MENT that maintains muscle and gonadotropins does not maintain prostate and seminal vesicles. The action of other 7 alpha-methylated androgens were similar to that of MENT. The importance of 5 alpha reductase in the differential action of testosterone and MENT on prostate was confirmed by using a 5 alpha-reductase inhibitor. The activity of testosterone was significantly suppressed in the ventral prostate and seminal vesicles but not on muscle by the 5 alpha-reductase inhibitor (N,N-diethyl-3-oxo-4-aza-5 alpha-androst-1-ene-17 beta-carboxamide). The enzyme inhibitor, however, had no influence on the activity of MENT on either tissue. In contrast, cyproterone acetate, an antiandrogen that competitively binds to the androgen receptors, inhibited the action of MENT and of testosterone on the prostate as well as on the muscle. In conclusion, these observations show that 7 alpha-methylated androgens can maintain muscle mass and normal gonadotropin levels in androgen deficient rats without hyperstimulating the prostate. These findings suggest that 7 alpha-methylated androgens may offer some health benefits to men who require androgen treatment.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1996

Androgens markedly stimulate the accumulation of neutral lipids in the human prostatic adenocarcinoma cell line LNCaP.

Microscopic evaluation of LNCaP cells stained with the lipophilic dye Oil red O revealed that androgens induce a marked stimulation of lipid droplet accumulation. As determined by quantitative analysis of the Oil red O extracted from the stained cells, stimulatory effects of the synthetic androgen R1881 became apparent at concentrations as low as 10(-11) M. Maximal induction (15-fold) was reached at 10(-8) M. Increases were observed 2 days after hormone addition and were maximal 1 day later. Accumulation of lipid droplets was also induced by mibolerone (another synthetic androgen) and by the natural androgens testosterone and dihydrotestosterone. In agreement with the aberrant ligand specificity of the mutated androgen receptor in LNCaP cells, stimulation of lipid accumulation was also apparent after treatment with progesterone and estradiol. Cortisol and the synthetic glucocorticoid dexamethasone were ineffective. The androgen antagonist Casodex (bicalutamide) abolished the stimulatory effect of R1881, further supporting the involvement of the androgen receptor. In agreement with this conclusion, no changes in lipid accumulation were observed after androgen treatment of the androgen receptor-negative prostate tumor lines PC-3 and DU-145. To investigate the nature of the lipids affected by androgens, lipid extracts were analyzed by TLC, complemented with enzymatic lipid analyses. Androgens were shown to have major effects on the content of triglycerides and cholesterol esters (33- and 7-fold stimulation, respectively), the two main classes of lipids stained by Oil red O. Phospholipid and cholesterol contents were increased by a factor of 2. Incorporation studies with [2-14C]acetate revealed that androgens caused a major stimulation of 2-14C incorporation into triglycerides and cholesterol esters (11- and 13-fold, respectively), suggesting that androgens act at least in part at the level of lipid synthesis. Taken together, these findings indicate that androgens, besides affecting proliferation and protein secretion, also markedly stimulate the production and accumulation of neutral lipids, revealing a novel interesting aspect of androgen regulation of LNCaP cells.

Adenocarcinoma↗
PubMed1997

Androgen-induced inhibition of proliferation in human breast cancer MCF7 cells transfected with androgen receptor.

Sex steroids control the proliferation of their target cells through two different pathways: 1) proliferative response (Step-1); and 2) inhibition of cell proliferation (Step-2). Mechanisms of cell proliferation regulation are incompletely understood; however, there is general agreement with the notion that sex steroid receptors play an important role in the control of the proliferation of sex steroid target cells. To test this hypothesis, a full human androgen receptor (AR) vector was transfected into human breast cancer MCF7 cells. The cloned cells that stably express the AR, called MCF7-AR1 cells, contained approximately five times more AR than the wild-type MCF7 cells from which they were derived. These AR-transfected cells retained their capacity to proliferate when estrogens were added to 10% charcoal-dextran stripped human serum but did not acquire the ability to proliferate when androgens were added to this medium. In serumless medium (ITDME), these cells proliferated maximally, as MCF7 cells did; however, natural and synthetic androgens prevented the AR-transfected cells from proliferating. Inhibition of cell proliferation occurred when physiological androgen concentrations (1 nM) were added to ITDME; this effect was almost completely reversed by Casodex, a synthetic androgen antagonist. Under the effect of androgens added to ITDME, MCF7-AR1 cells were arrested in the G0/G1 phase within 24 h. These data suggest that: 1) the androgen-induced inhibition of cell proliferation (Step-2) is AR-mediated; and 2) the AR may be necessary, but not sufficient, to mediate the androgen-induced proliferative response (Step-1).

Androgen Antagonists↗