The androgenic regulation of superhelical-DNA nicking-closing enzyme in rat ventral prostate.

The activity of superhelical-DNA nicking-closing enzyme (NC enzyme) was measured in nuclei from rat ventral prostate by a fluorimetric assay based on the binding of ethidium bromide to supercoiled phage-PM2 DNA. The nuclear concentration of NC-enzyme activity declined rapidly after castration, although this response could be prevented by daily administration of dihydrotestosterone. The low NC-enzyme activity in involuted prostates (10% of normal) was restored to normal after 8-10 days of treatment with androgen. In the regenerating prostate the time course of restoration of NC-enzyme activity was not in phase with that of DNA synthesis. Examination of nucleosome repeat lengths and the arrangement of nucleosomes along the chromatin fibre revealed no differences in the structural organization of chromatin in prostates with high or low NC-enzyme activity. Together, these results suggest that the major role of NC enzyme is related to the onset and maintenance of differentiation in the prostate and that the activity of this enzyme is not expressed through gross alterations in chromatin structure.     

Isoenzymes of glutathione transferase in rat small intestine.

The role of plasminogen activators (PAs) as potential mediators of involution of the rat ventral prostate was investigated by using an approach involving the administration in vivo of anti-PA drugs. The prostates of castrated rats, which had been injected daily for 7 days with the anti-PA drugs 6-aminohexanoic acid, tranexamic acid, aprotinin and cortisol, were assayed for PA activity, weight and cell number. In the prostates from the castrated controls, there was a 10-fold increase in the mean PA activity and a 7-fold decrease in cell number relative to that of the non-castrated animals. Although this rise in enzyme activity could be decreased to some extent by all the drugs except aprotinin, only treatment with high doses of tranexamic acid or cortisol had a statistically significant effect. A similar pattern was observed with respect to the relative potency of the drugs in preventing the loss of prostatic weight and cell number after castration. The effects of cortisol were dose-dependent, with complete inhibition of both the rise in PA activity and cell loss occurring at a dose of about 15 mg/day. Since the concentration of the principal intranuclear androgen, dihydrotestosterone, was the same in the prostates from treated and untreated castrated rats, the effects of cortisol are not due to increased retention of this androgen. Rather, the high inverse correlation (r = 0.86) between the cellular concentration of PA activity and the cell population of the prostate implies that PAs are directly associated with prostatic involution and that cortisol, and to a lesser extent tranexamic acid, blocks the involution process through inhibition of PAs.     

The dependence of the incorporation of methamphetamine into rat hair on dose,frequency of administration and hair pigmentation

In this paper, the incorporation of methamphetamine (MA) into rat hair was studied. The main purpose of this study was to investigate whether MA can be detected or positive hair results can be obtained in hair of rats administered a single dose of MA. The relationship between dose and frequency of administration and the concentrations of MA and its metabolite, amphetamine (AP), in rat hair were evaluated and the MA and AP concentrations in white and pigmented hair were compared. MA was administered to rats as follows: low dose (0.5 mg/kg/day), medium dose (2 mg/kg/day) and high dose (10 mg/kg/day). The frequency of administration was one time per day for 1, 2, 3, 4, 5, 15 and 30 days. Hair and urine samples were collected from rats and analyzed by gas chromatography/mass spectrometry (GC/MS). MA could be identified in pigmented rat hair when MA was administered for 4 or more days at low daily dose and on day 1 following administration of medium and high daily doses. Positive results for MA were obtained from pigmented rat hair when MA was administered for 30 days at low daily dose, for 4 or more days at medium daily dose, or for 2 or more days at high daily dose. The concentrations of MA and AP found in rat hair were proportional to the dose and frequency of administration. The concentrations of MA and AP in pigmented rat hair were 2–10 times higher than those in white rat hair. The results of this study on the incorporation of MA into rat hair can serve as a model to better understand the incorporation of MA into human hair even though there are differences between animal models and human hair.     

Androgen dependence of specific kallikrein gene family members expressed in rat prostate

We have used oligonucleotide probes specific for members of the rat kallikrein/tonin gene family (PS, S1, S2, S3, K1, and P1) to establish which arginyl esteropeptidase (kallikrein-like) genes are expressed in the prostate. We have also compared the expression and androgen dependence of these genes in prostate, submaxillary gland (SMG) and kidney. Only S3 (tonin-like) and P1 (kallikrein-like) are expressed in the prostate, with S3 very much more abundant. Prostatic S3 mRNA disappears after 8 days castration and is restored to intact levels by dihydrotestosterone (DHT) but not estradiol benzoate (EB) for 8 days. Prostate P1 mRNA levels were similarly but not identically affected. All six genes are expressed in the SMG, with PS (true kallikrein) the most abundant. Levels of PS mRNA in SMG are unaffected by castration, DHT, or EB treatment, although mRNA levels of other kallikrein-like (S1, K1, and P1), tonin (S2), and tonin-like (S3) genes fall 40-60% after castration, and are unaffected or partially restored by DHT and/or EB administration. Only PS and K1 are expressed in the kidney, at much lower levels than in the SMG and unaffected by castration or steroids. These studies thus confirm and extend the concept of tissue specificity of arginyl esteropeptidase gene expression, and further demonstrate that the same gene(s) is differentially regulated by androgens in the rat prostate, SMG, and kidney.     

The stimulatory effect of testosterone propionate and 17β-estradiol on 5′-methylthioadenosine phosphorylase activity in rat target tissues

The effect of castration and subsequent administration of 17β-estradiol and testosterone propionate on 5′-methylthioadenosine phosphorylase activity in rat target tissues was studied. Castration 34 days earlier resulted in a 95 reduction in ventral prostate 5′-methylthioadenosine phosphorylase activity and 16 days earlier in a 67% reduction in uterine 5′-methylthiodenosine phosphorylase activity. Four days of testosterone propionate administration stimulated ventral prostate 5′-methylhioadenosine phosphorylase activity 32% above castrate levels, which represented more than 50% of the intact control levels. 17β-Estradiol on the other hand stimulated uterine 5′-methylthioadenosine phosphorylase activity of 35% above castrate controls within 24h and with 3 days of continuous hormone treatment to within 97% of the intact control levels. However, castration and subsequent 17β-estradiol administration did not affect 5′-methylthioadenosine phosphorylase activity in rat liver and lung. Both prostate and uterine 5′-methylthioadenosine phosphorylase were shown to metabolize 5′-methylthioadenosine to 5′-methylthioribose through a 5′-methythiribose 1-phosphate intermediate. The data suggest that 5′-methylthioadenosine is not allowed to accumulate in rat target tissues even under conditions which are known to stimulate polyamine synthesis.     

Antiandrogenic and apoptotic effects of RU-486 on animal prostate

Mifepristone (RU-486) is a potent antagonist of steroid hormone receptors such as glucocoticoid and progesterone receptors. This compound also is a very strong inducer of the interaction between androgen receptors and corepressors NCoR and SMRT and therefore could be used as selective receptor modulator.

In this study we determined the relative binding affinity of RU-486 to androgen receptors (AR) obtained from rat prostate cytosol as well as the in vivo effect of different doses of RU-486 on the prostate weight of hamsters treated with dihydrotestosterone and/or RU-486. We determined also the prostate cell death (apoptosis) in hamster treated with, dihydrotestosterone (DHT) and/or RU-486.

The results of this study indicated that the relative binding affinity of RU-486 for AR is 4.3%. The data from the in vivo experiments also showed that RU-486 inhibited the prostate weight significantly in the highest doses thus indicating the antagonistic action of this compound on hamster prostate.

The immunohistochemistry analysis showed that after 1 month of castration, the hamster prostate was atrophic. Treatment with DHT produced epithelial cell activity (measured by the increase in the prostate weight) and very low rate of apoptosis. When DHT was administered together with RU-486 (10 mg/kg) no change was observed. On the other hand, DHT plus higher doses of RU-486 (40, 80 mg/kg) resulted in an increase of apoptosis in stromal and secretory epithelial cells. In addition to the increase of the prostate cell apoptosis produced by the treatment with high dose of RU-486, other factors could contribute to the decrease of the prostate weight observed. Another possibility could be a reduction in the ductal fluid due to poor epithelial cell secretory activity more than apoptosis itself. Furthermore, in this experiment, RU-486 could have inhibited the growth of the prostate gland produced by DHT in a greater extent than the induction of atrophy and cell death. This fact could depend on the doses used, due to the low affinity of this compound for the androgen receptors.     

Differential effect of testosterone and dihydrotestosterone on the sexual behavior of prepuberally castrated male rabbits

The effect of testosterone propionate (Tp) and dihydrotestosterone propionate (DHTp) at doses of 1, 3 and 9 mg daily for 30 days on the copulatory behavior of prepuberally castrated male New Zealand white rabbits was studied. Tp was significantly more effective than DHTp in eliciting copulatory behavior at each dose level tested. Three milligrams Tp was the minimal dose required to elicit mounting consistently. DHTp at the high dose level (9 mg) only elicited sexual activity comparable to that observed with the low dose of Tp (1 mg). The results suggest that T does not need to be reduced to DHT to stimulate sexual behavior in the male rabbit.     

Differential effects of the anti-estrogen MER-25 and of three 5alpha-reduced androgens on mounting and lordosis behavior in the rat.

Four experiments were performed in order to evaluate further the hypothesis that androgen must be aromatized to estrogen for the activation of masculine sexual behavior in the male rat. In Experiment 1 it was found that the anti-estrogen MER-25 failed to disrupt mounting behavior in castrated males which simultaneously received testosterone propionate (TP). However, in Experiment 2 it was found that MER-25 as weil as 3β-androstanediol effectively activated masculine behavior in castrated males treated simultaneously with dihydrotestosterone propionate. Both MER-25 and 3β-androstanediol had previously been shown to display an affinity for cytoplasmic estradiol-17β receptors present in male rat anterior hypothalamus. In Experiments 3 and 4, performed with ovariectomized females, it was found that whereas MER-25 antagonized the stimulatory effect of estradiol benzoate (EB) on lordosis behavior, 3β-androstanediol did not. In addition, 5α-dihydrotestosterone and 3α-androstanediol, two compounds which had previously been shown to have almost no affinity for estradiol-17β receptors in the hypothalamus, both inhibited the stimulatory effect of EB on lordosis. It is concluded that the fact that anti-estrogens suppress lordosis induced in females with either EB or TP, but fail to disrupt TP-induced mounting behavior in male rats does not argue against the aromatization hypothesis for masculine sexual behavior.     

Effect of estradiol on the metabolism of testosterone by rat prostate

Prostatic tissue from normal, estradiol-treated, and castrated rats was incubated with testosterone, and the metabolites formed were studied. Pretreatment with estradiol-17β did not affect the total amount of testosterone metabolized per unit weight of tissue. In contrast, the total amount of testosterone metabolized was significantly reduced following castration. The formation of dihydrotestosterone (17β-hydroxy-5α-androstan-3-one; DHT) was not affected by treatment with estradiol, but was significantly reduced by previous castration. Estradiol treatment enhanced the formation of 17-keto metabolites of testosterone by the prostate, giving lower 17-hydroxy to 17-keto ratios than incubations with prostates from control or castrated rats. These results are consistent with the theory that the mechanisms leading to the involution of prostate after estradiol treatment and after castration are different.     

Potent CYP17 inhibitors: improved syntheses, pharmacokinetics and anti-tumor activity in the LNCaP human prostate cancer model

A facile preparation of azolyl steroids, VN/85-1 and VN/87-1 (potent inhibitors of CYP17) has been developed. This process without tedious chromatographic separations improved the overall yields from 55 and 45% to 70 and 65% for VN/85-1 and VN/87-1, respectively. Pharmacokinetic studies of VN/85-1 were conducted in male SCID mice. Following subcutaneous (s.c.) administration of 100mg/kg of VN/85-1, peak plasma level of 16.73 microg/ml occurred after 45 min, and the compound was cleared rapidly with a t(1/2) of 52.34 min. The bioavailability of VN/85-1 after s.c. administration was 83.0%. VN/85-1 was also rapidly metabolized to the corresponding 3-oxo-4-ene analog, 17-(1H-imidazol-1-yl)androsta-4,16-diene-3-one (VN/108-1). In our attempt to optimize the anti-tumor efficacy of these two CYP17 inhibitors, we studied their anti-tumor efficacies in male SCID mice bearing LNCaP tumor xenografts, utilizing various drug doses and drug scheduling. Three times a day dose regimen (3 x dose regimen) of VN/85-1 was more effective than a once daily dose. In contrast, 3 x dose regimen doses of VN/87-1 were less effective than the once daily dose. However, at their effective dosage regimes, VN/85-1 and VN/87-1 were each as effective as castration and more effective than finasteride or casodex, an anti-androgen used for prostate cancer (PC) therapy. For all of the treatments, there was a strong correlation between the tumor volumes and other associated parameters, such as, tumor weights, and serum testosterone (T) and PSA levels. These results indicate that VN/85-1 or VN/87-1 may be useful in the treatment of hormone-dependent prostate cancer.     

Gonadal steroids and anterior lobe dynorphin in the male rat

Immunoreactive (ir)-dynorphin levels were measured, and the species characterized by high performance liquid chromatography (HPLC), in the pituitary and hypothalamus of intact and castrate male rats. On HPLC, ir-dynorphin co-eluted with authentic dynorphin A 1-8, dynorphin A 1-17 and dynorphin 1-32 in the hypothalamus and intermediate lobe; in two different reversed phase (RP)-HPLC systems, anterior lobe ir-dynorphin co-eluted uniquely with dynorphin 32 (4K dynorphin). Anterior lobe levels of total ir-dynorphin were significantly lowered 7 days after castration, while HPLC profiles in all tissues remained unchanged. The change in anterior pituitary ir-dynorphin levels was reversed in a dose-related manner by dihydrotestosterone (15-500 micrograms/100 g b. wt/day); estradiol benzoate (3 micrograms/100 g/day) was without effect. The changes on castration and androgen administration suggest that gonadal steroids play a role in the regulation of dynorphin, as well as gonadotrophins and prolactin, within the anterior pituitary gland.     

Inhibition of two rat hepatic microsomal drug-metabolizing enzymes by a carcinogenic N-nitrosated pesticide: N-nitrosocarbaryl

N-Nitrosocarbaryl (N-methyl-1-naphthyl N-nitrosocarbamate) was intraperitoneally administered to male and female rats on four consecutive days at the following doses: 6.25 mg, 12.5 mg, 25 mg and 50 mg/kg body weight/day in olive oil solution; the controls received just the oil. In a second experiment, a daily intraperitoneal dose of 25 mg/kg of N-nitrosocarbaryl was given for 1, 2, 3 or 4 days; the animals were killed 24 h after the last treatment. The two following microsomal enzymatic activities were assayed: aniline aromatic hydroxylase and p-nitroanisole O-demethylase; the levels of cytochrome P-450, proteins and RNA were measured in the hepatic microsomal fraction. N-Nitrosocarbaryl is an inhibitor of the two investigated microsomal monooxygenases at doses of 25 and 50 mg/kg when administered on 4 consecutive days. During the daily administration, enzyme inhibition is seen in females after one day of treatment whereas cytochrome P-450 only becomes lowered after 4 days of administration. In males, no modification of this parameter is observed whereas the activities of microsomal monooxygenases are inhibited. These results suggest that N-nitrosocarbaryl could act on the active sites of the enzymes which metabolize aniline and p-nitroanisole.     

Expression cloning and regulation of steroid 5 alpha-reductase, an enzyme essential for male sexual differentiation

The conversion of testosterone into the more potent androgen, dihydrotestosterone, catalyzed by the enzyme steroid 5 alpha-reductase, is required for the differentiation of male external genitalia. Here, we report the isolation of cDNA clones encoding the rat steroid 5 alpha-reductase using expression cloning in Xenopus oocytes. DNA sequence analysis demonstrates that the liver and ventral prostate forms of steroid 5 alpha-reductases are identical hydrophobic proteins of 29 kDa. The amount of steroid 5 alpha-reductase mRNA in liver increased in response to castration, but remained unchanged in the prostate. Testosterone administration to castrates induced expression of mRNA in the prostate but had no effect on liver. The data suggest that the steroid 5 alpha-reductase gene is differentially regulated by testosterone in androgen-responsive versus non-responsive tissues.     

Effects of testosterone metabolites on serum gonadotropin concentrations in immature male rats.

The ability of testosterone, androsterone, 5alpha-androstane-3alpha,17beta-diol, and 5alpha-androstane-3beta,17beta-diol to prevent the castration-induced rise in serum gonadotropin levels was investigated in immature male rats. Rats castrated at 30 days of age were treated once per day by subcutaneous injection of 12.5-100 mug of the steroid per 100 g body weight per day for 3 days, beginning on the day of castration. The animals were sacrificed 24 h after the last injection. Testosterone propionate, androsterone propionate, and 5alpha-androstane-3alpha,17beta-diol dipropionate were also tested at the approximate molar equivalent of 100 mug of the free alcohol form per 100 g body weight per day. Testosterone propionate and 5alpha-androstane-3alpha,17beta-diol were the only compounds tested that prevented the castration induced rise in luteinizing hormone (LH) concentrations. Testosterone propionate also inhibited the rise in follicle stimulating hormone (FSH) concentrations whereas 5alpha-androstane-3alpha,17beta-diol inhibited the rise in FSH in one but not in another experiment. These were the only compounds tested that affected serum FSH concentrations. The lower doses of testosterone tested significantly increased serum LH, but not FSH concentrations compared to castrate control animals. The highest dose tested partially inhibited the rise in serum LH concentrations. Both androsterone and androsterone propionate maintained ventral prostate weights. Although neither compound prevented the castration induced rise in serum LH, two groups receiving androsterone had serum LH concentrations significantly lower than the castrate control group. 5alpha-Androstane-3beta,17beta-diol and 5alpha-androstane-3alpha,17beta-diol dipropionate failed to maintain ventral prostate weights or prevent the rise in serum gonadotropin levels. These results indicate that 5alpha-androstane-3alpha,17beta-diol is capable of preventing the castration induced rise in serum LH concentrations in the immature male rat and thus may participate in the regulation of LH secretion in these animals.     

Anabolic effects of testosterone are preserved during inhibition of 5alpha-reductase

At replacement doses, testosterone produces only modest increases in muscle strength and bone mineral density in older hypogonadal men. Although higher doses of testosterone are more anabolic, there is concern over increased adverse effects, notably prostate enlargement. We tested a novel strategy for obtaining robust anabolic effects without prostate enlargement. Orchiectomized (ORX) male rats were treated for 56 days with 1.0 mg testosterone/day, with and without 0.75 mg/day of the 5alpha-reductase inhibitor MK-434. Testosterone administration elevated the prostate dihydrotestosterone concentration and caused prostate enlargement. Both effects were inhibited by MK-434. ORX produced a catabolic state manifested in reduced food intake, blunted weight gain, reduced hemoglobin concentration, decreased kidney mass, and increased bone resorption, and in the proximal tibia there was both decreased cancellous bone volume and a decreased number of trabeculae. In soleus and extensor digitorum longus muscles, ORX reduced both the percentage of type I muscle fibers and the cross-sectional area of type 1 and 2 fibers. Testosterone administration caused a number of anabolic effects, including increases in food intake, hemoglobin concentration, and grip strength, and reversed the catabolic effects of ORX on bone. Testosterone administration also partially reversed ORX-induced changes in muscle fibers. In contrast to the prostate effects of testosterone, the effects on muscle, bone, and hemoglobin concentration were not blocked by MK-434. Our study demonstrates that the effects of testosterone on muscle and bone can be separated from the prostate effects and provides a testable strategy for combating sarcopenia and osteopenia in older hypogonadal men.     

Effects of dihydrotestosterone and estradiol benzoate pretreatment upon testosterone-induced sexual behavior in the castrated male rat

Three groups of inexperienced castrated male rats were treated daily for 15 days with oil, estradiol benzoate (1 μg), or dihydrotestosterone (1 mg), and thereafter injected daily with testosterone (1 mg) for 21 days. Sexual behavior was tested every third day after the start of the pretreatment until day 36. Estradiol benzoate or dihydrotestosterone failed to elicit sexual behavior. Pretreatment with dihydrotestosterone, but not estradiol benzoate, significantly shortened the intervals to initiation of mounting and intromission in response to testosterone. The results suggest that fully developed genitals (penis and/or sexual accessories) facilitate initiation of copulatory behavior in response to testosterone administration.     

Studies of the 3beta-hydroxysteroid oxidoreductase activity in rat ventral prostate

The reduction of ³H-androstanolone into 3β-androstanediol was used to study the 3β-hydroxysteroid oxidoreductase activity of rat ventral prostate. This activity is present only in the cytosol and has a pH optimum of 8.5 with NADH as cofactor. The 3β-hydroxysteroid oxidoreductase activity , as compared to 3α-hydroxysteroid oxidoreductase activity, is much lower in the present study than was observed previously during prostate perfusion $\text{in vivo}$ or prostate organ culture superfusion.