Growth Of Ventral Prostate Research Articles

Transforming growth factor-beta1 (TGF-beta1) in penile and prostate growth in the rat during sexual maturation.

The goal of this study was to determine whether transforming growth factor-beta1 (TGF-beta1) may contribute to the arrest of penile growth and the down-regulation of androgen receptors (AR) that occur during sexual maturation in the rat penis. For this purpose, body, penis, and prostate weights were obtained from male rats of increasing ages, and penis and prostate TGF-beta1 concentrations were determined by a sandwich enzyme-linked immunosorbent assay. The cytosol fraction was obtained from the shafts and glandes of immature (19-day-old) and adult (90-day-old) rat penises, and ARs were measured by a western blot assay. The effect of exogenous TGF-beta1 on penile growth was examined in vivo in two groups of immature rats (21 and 27 days old) implanted with miniosmotic pumps delivering either human TGF-beta1 or vehicle only directly into the corpora cavernosa for 6 days. The penises, prostates, and testes were weighed, and the AR content was estimated by western blot. The growth rate of the penis declined after 8 weeks of age, whereas the ventral prostate growth rate increased until 14 weeks of age and then slowed down. The content of penile AR protein decreased seven-fold in the adult rats compared to the immature animals. Penile TGF-beta1 concentration increased nearly three-fold from the 19-day-old rats to a peak at 60 days of age and then decreased over the next 4 months to the initial levels. In contrast, TGF-beta1 concentration in the prostate was not significantly affected by age and remained below the lowest penile values in all age groups. Transforming growth factor-beta1 given locally to the penis reduced penile shaft weight by 38 and 22% in two groups of immature rats, while the weights of the penile glans, testis, and ventral prostate remained unaffected. Androgen receptor content was higher in the glans than in the shaft and was not changed by TGF-beta1 treatment. These results suggest that the increase of TGF-beta1 levels in the penis may reinforce growth arrest caused by the down-regulation of penile ARs, whereas the maintenance of a high content of ARs and a low TGF-beta1 concentration may allow prostate growth to continue.

Effects of Steroid 5α-Reductase Inhibitor ONO-9302 and Anti-Androgen Allylestrenol on the Prostatic Growth, and Plasma and Prostatic Hormone Levels in Rats

—ONO-9302 [epristeride; (-)-17β-(tert-butylcarbamoyl)androsta-3,5-diene-3-carboxylic acid] is a novel inhibitor of steroid 5α-reductase. We studied in vitro and in vivo effects of ONO-9302 on the rat prostatic tissue in comparison with those of the anti-androgen allylestrenol. ONO-9302 inhibited the rat prostatic enzyme with an IC50 value of 11 nM, whereas allylestrenol was about 80,000-fold less potent. The growth of ventral prostate, which was induced by the subcutaneous injection of testosterone propionate in the castrated rats, was significantly reduced by ONO-9302 at oral doses of 1 -100 mg/kg/day. Allylestrenol showed a significant effect only at a dose of 100 mg/kg/day. In mature male rats, ONO-9302 significantly reduced the ventral prostate weight at doses of 10-100 mg/kg/day and decreased prostatic 5α-dihydrotes-tosterone (DHT) content associated with a rise in testosterone (T) content at doses of 0.1 -100 mg/kg/day. Plasma hormone levels (i.e., T, DHT, luteinizing hormone (LH) and follicle stimulating hormone (FSH)) were not altered significantly. Allylestrenol significantly reduced the ventral prostate weight at doses of 10-100 mg/kg/day. However, unlike ONO-9302, allylestrenol reduced both the prostatic DHT and T contents and also lowered plasma T, DHT, LH and FSH levels at a dose of 30 mg/kg/day. These results suggest that ONO-9302 reduces the prostatic growth by inhibiting the conversion of T to DHT in the prostate without lowering blood T level unlike anti-androgen drugs.

Inhibitors of collagen synthesis and hypophysectomy: effects on androgen induced growth of ventral prostate in rats.

To elucidate the effect of decreased amounts of collagen on prostatic growth, beta-aminopropionitrile, one of the agents that selectively inhibit collagen formation, was administered, with or without exogenous androgen and/or hypophysectomy, to rats of varying ages. The weight of the ventral prostate and the collagen content and the ratio of type III to type I collagen in the ventral prostate were examined. Administration of beta-aminopropionitrile, with or without exogenous androgen, reduced the collagen content in the ventral prostate in any age groups, but increased the weight of the ventral prostate only in young rats. Administration of beta-aminopropionitrile to hypophysectomized rats did not change the weight and collagen content. Administration of beta-aminopropionitrile prevented androgen-induced growth of prostatic collagen, resulting in increased prostatic weight in young rat. The ratio of type III to type I collagen in the rat ventral prostate remained unchanged by administration of beta-aminopropionitrile, exogenous androgen, hypophysectomy, or advancing age. It would appear that in young rats prostatic collagen plays an important role in suppressing prostatic growth. The ratio of type III to type I collagen is stable under various experimental conditions in the ventral prostate.

FCE 28260, a new 5 alpha-reductase inhibitor: in vitro and in vivo effects.

FCE 28260 is a novel inhibitor of 5 alpha-reductase (5 alpha R), the enzyme responsible for the conversion of testosterone (T) to 5 alpha-dihydrotestosterone (DHT). The compound caused inhibition of rat and human prostatic enzymes, with IC50 values of 15 and 16 nM, respectively, compared to the values of 30 and 52 nM shown by finasteride. Furthermore, FCE 28260 was highly potent in inhibiting human recombinant 5 alpha R type 2 and 1 isozymes, showing IC50 values of 3.3 and 36 nM, and therefore it was more potent than finasteride (IC50 values of 8.5 and 470 nM) on both isozymes. In prepubertal, T-implanted castrated rats, FCE 28260, given orally for 7 days, reduced ventral prostate growth with an ED50 of 0.8 mg/kg, i.e. five times lower than that shown by finasteride. No anti-androgenic activity in DHT-implanted castrated rats was found up to 10 mg/kg/day. In adult male rats, FCE 28260 reduced prostatic DHT concentrations 6 h after oral dosing with a potency similar to that of finasteride (65% reduction at 1 mg/kg) but was found to be markedly more potent than the reference compound at 24 h (74% reduction in prostate DHT at 10 mg/kg, compared to 26% reduction induced by finasteride). These results indicate that FCE 28260 represents a marked improvement over finasteride.

The preclinical development of bicalutamide: pharmacodynamics and mechanism of action

Objectives. To describe the preclinical development of bicalutamide and clarify its pharmacodynamics and mechanism of action. Bicalutamide was developed from a series of nonsteroidal compounds related to flutamide that showed a range of pharmacologic activity from full androgen agonist to pure antiandrogen, including progestational and antiprogestational properties. Methods and Results. Bicalutamide is a pure antiandrogen that binds to rat, dog, and human prostate; the affinity compared with the natural ligand 5α-dihydrotestosterone is low, but bicalutamide has an affinity for the rat androgen receptor approximately four times higher than hydroxyflutamide, the active metabolite of flutamide. Bicalutamide also binds to androgen receptors found in the LNCaP human prostate tumor and the Shionogi S115 mouse mammary tumor cell line, as well as androgen receptors transfected into CV-1 and HeLa cells. In all cases, bicalutamide behaves as a pure antiandrogen and inhibits gene expression and cell growth stimulated by androgen. Studies with the LNCaP cell line are particularly interesting, as these cells contain a mutated androgen receptor (codon 868, Thr → Ala), which behaves idiosyncratically with other antiandrogens (cyproterone acetate and flutamide): both these antiandrogens act as agonists in this cell line and stimulate proliferation. Studies in vivo show that bicalutamide is a potent antiandrogen in the rat. In immature, castrated male rats treated daily with testosterone propionate, bicalutamide produces a profound inhibition of accessory sex organ (ventral prostate and seminal vesicles) growth at oral doses as low as 0.25 mg/kg; it is more active in this test than flutamide or cyproterone acetate. In mature male rats, daily oral doses of bicalutamide produce a dose-related reduction in weights of the ventral prostate glands and seminal vesicles: in this test, bicalutamide is around five times as potent as flutamide. In contrast to flutamide, which produces dose-related, marked increases in serum luteinizing hormone (LH) and testosterone as a consequence of the central inhibition of the negative feedback effects of androgens on the hypothalamic—pituitary—testes axis, bicalutamide has little effect on serum LH and testosterone; i.e., it is peripherally selective. The peripheral selectivity of bicalutamide in the rat is not due to differences between the prostate versus hypothalamic or pituitary receptors, as bicalutamide reverses the suppressive effect of testosterone on luteinizing hormone-releasing hormone (LHRH) secretion from hypothalamic slices in vitro and is as effective as flutamide at sensitizing the pituitary gland to secrete LH in response to administered LHRH. The peripheral selectivity of bicalutamide has now been shown to be due to poor penetration across the blood—brain barrier: tissue distribution studies with [ 3H]bicalutamide show that although it is concentrated in the organs of metabolism and secretion as well as in the prostate, the pituitary glands, and the seminal vesicles, levels in the hypothalamus and the central nervous system (CNS) are much lower than in blood. Indeed, it is probable that levels found in the CNS reflect levels of blood contamination. In dogs, bicalutamide has exquisite potency and causes dose-related atrophy of the prostate gland and epididymides; with an oral ED 50 of 0.1 mg/kg, it is around 50 times as potent as flutamide in this species and also more potent than the steroidal antiandrogen WIN49596 and the 5α-reductase inhibitor MK-906. Even at substantial multiples of the active dose (up to 100 mg/kg orally), bicalutamide failed to increase serum testosterone, so it is also peripherally selective in the dog. Magnetic resonance imaging studies have shown that bicalutamide is also a potent antiandrogen in the monkey; oral doses of 1 and 5 mg/kg produced significant reductions in seminal vesicle and ventral prostate size. At a daily oral dose of 25 mg/kg, bicalutamide effected a highly significant reduction in growth of Dunning R3227H transplantable rat prostate tumors that was equivalent to that achieved by either surgical castration or medical castration with the LHRH agonist goserelin acetate. In a comparative study, flutamide was shown to be both less potent and less active than bicalutamide. In all these preclinical studies, bicalutamide was well tolerated. It had no significant effects in any general pharmacology tests except in the dog, in which, on chronic administration, it caused a small increase in heart rate and a reduction in PR interval at doses of >25 times the ED 50 value for prostate atrophy. Because there was neither impairment of cardiac function nor pathologic observations when cardiac histology was examined in chronic toxicity studies, it is concluded that this idiosyncratic finding is of no toxicologic consequence. Conclusions. Bicalutamide was shown to be a pure antiandrogen and specifically did not possess estrogenic or anestrogenic, progestational or antiprogestational, glucocorticoid or antiglucocorticoid, or mineralocorticoid or antimineralocorticoid activity in classic endocrine tests. Bicalutamide also showed no androgenic activity and did not inhibit steroid 5α-reductase.

An orthotopic model for the study of growth factors in the ventral prostate of the rat: effects of epidermal growth factor and basic fibroblast growth factor.

In order to determine if epidermal growth factor (EGF) or basic fibroblast growth factor (bFGF) are capable of stimulating prostatic growth in situ, we complexed EGF and bFGF to a Matrigel (MG) vehicle that was subsequently injected orthotopically into the ventral prostate of adult rats. Three weeks following a single injection of 0.1 ng of EGF or bFGF, the wet weight of the growth factor-injected lobes of the ventral prostate was increased (P < or = 0.025) 144 +/- 14% and 138 +/- 8%, respectively compared to contralateral lobes injected with MG only. Total DNA and protein per lobe (P < or = 0.025) and the incorporation of bromodeoxyuridini (BrdUrd; P < or 0.01) were all significantly increased in lobes injected with EGF or bFGF compared to MG-injected lobes. Thus, EGF and bFGF were stimulating true growth of the rat ventral prostate in situ. The induced prostatic growth was ligand specific, because co-injection with neutralizing antibodies abolished EGF and bFGF stimulation of prostatic wet weight. The effect of a single injection of 0.1 ng of growth factor was long-lasting and elevated prostatic wet weight for 4 (P < or = 0.05; bFGF) to 6 (P < or = 0.05; EGF) weeks. Histologic evaluation did not reveal any gross changes in the ratio of stroma to epithelium in either EGF- or bFGF-injected lobes at the 0.1 ng/lobe dose. A slight hyperplasia of the prostatic epithelium was detected in lobes injected with 10 ng of EGF. Of note, the incorporation of BrdUrd was primarily localized in the luminal and basal epithelial cells, whereas incorporation into the prostatic stroma was scanty in lobes injected with either EGF or bFGF. In summary, we have developed an orthotopic model enabling the study of the roles of growth factors in prostatic physiology, function, and disease in situ. Additionally, we have demonstrated that when injected orthotopically into the rat ventral prostate, EGF and bFGF stimulate the growth of the prostatic epithelium to similar degrees.

Endocrine properties of the testosterone 5α-reductase inhibitor turosteride (FCE 26073)

Turosteride was tested in a series of studies for its effect on 5α-reductase and for its possible influence on other steroidogenic enzymes and on steroid receptors. The compound was found to inhibit human and rat prostatic 5α-reductases with IC 50 values of 55 and 53 nM, respectively, whereas it caused a less marked inhibition of the dog enzyme (IC 50 2.2 μM). Turosteride showed no relevant effect on rat adrenal C 20,22-desmolase (IC 50 254 μM) and human placental aromatase (IC 50 > 100 μM), and only at relatively high concentrations it caused inhibition of human placental 5-ene-3β-hydroxysteroid dehydrogenase-isomerase (3β-HSD-I) (IC 50 2.5 μM). Turosteride was found to be a selective 5α-reductase inhibitor showing no noteworthy binding to receptors for androgens (relative binding affinity, RBA, 0.004%) estrogens (⩽ 0.005%), progesterone (< 0.005%), glucocorticoids (< 0.01%) and mineralocorticoids (< 0.03%). Its biochemical profile was similar to that of finasteride, whereas 4-MA (17 β- N, N-diethyl-carbamoyl-4-methyl-4-aza-5 α-androstan-3-one) was confirmed to be a non-selective 5α-reductase inhibitor, showing a degree of binding affinity to the androgen receptor (RBA 0.1%) and a marked inhibition of 3β-HSD-I (IC 50 32 nM). When given orally in immature castrated rats together with subcutaneous testosterone propionate (TP) for 7 consecutive days, turosteride reduced the ventral prostate and seminal vesicle growth promoting effect of TP, with IC 50 values of ≈ 5 and 6.7 mg/kg/day, whereas levator ani weight was unchanged. In comparison, 4-MA was approx. 3-fold less potent than turosteride in reducing the prostate and seminal vesicle weights and caused a marked reduction of levator ani weight, thus showing its unselectivity.

Evidence For A Non-Androgenic Role of Testis and Epididymis in Androgen-Supported Growth of the Rat Ventral Prostate

A widely held view is that the role of testis in prostatic growth is through its ability to secrete androgen. Our earlier observation suggested a non-androgenic role for the testis, and perhaps the epididymis, in promoting growth of the ventral prostate in rats. The present study was conducted to evaluate the separate role of the testis and the epididymis in this phenomenon. In the first study, increasing quantities of silastic tubing filled with crystalline testosterone were implanted into adult Sprague-Dawley rats at the time of bilateral epididymo-orchiectomy or sham-operation. Twenty-eight days later, growth of the ventral prostate, as determined by fresh weight, DNA, and protein content, was significantly greater in sham-operated rats than in those receiving combined epididymo-orchiectomy, confirming our previous observation using dihydrotestosterone. In the second and third studies, rats were subjected to selective surgical procedures to evaluate the independent role of the testis and the epididymis. At the same time, 12cm silastic tubing filled with testosterone or dihydrotestosterone were implanted subcutaneously into each of these animals for 28days. Results indicated that the ventral prostate was significantly smaller in rats receiving the combined epididymo-orchiectomy than that of sham-operated controls. Simple orchiectomy or simple epididymectomy resulted in an increased weight of the ventral prostate between the two values obtained from the above two groups. Ligation of either the efferent duct or the vas deferens yielded ventral prostatic weights comparable to the androgen-treated, sham-operated controls. These results indicated that in order to achieve a maximal effect on androgen-supported growth of the ventral prostate, the presence of both the testis and the epididymis is required. Accepted for publication February 10, 1992.

17β-acylurea derivatives of 4-azasteroids as inhibitors of testosterone 5α-reductase

A series of 17β-acylurea-4-aza-5α-androstan-3-one derivatives has been assayed in vitro as inhibitors of testosterone 5α-reductase, using the particulate fraction of human hyperplastic prostate and rat prostate as enzyme sources. The most active derivatives were 1-[4-methyl-3-oxo-4-aza-5α-androstane-17β-carbonyl]-1,3-dicyclohexylurea (compound 1) and 1-[4-methyl-3-oxo-4-aza-5α-androstane-17β-carbonyl]-1,3-diisopropylurea (compound 3) which demonstrated IC 50 values of 41 and 55 nM for the human enzyme and of 83 and 53 nM for the rat enzyme, respectively. Neither compound showed any relevant binding affinity to the rat prostate androgen receptor (IC 50 of ≈ 100 and 84 μM). When given orally in immature castrated rats together with subcutaneous testosterone propionate (TP) for 7 consecutive days, compound 3 (laboratory code FCE 26073), at 3 mg/kg/day, significantly decreased the ventral prostate growth promoting effect of TP by 40–50%, whereas compound 1 was ineffective up to the dose of 10 mg/kg/day.

Changes in follicle-stimulating hormone secretion in spontaneously hypertensive rats.

FSH and testosterone plasma levels, pituitary FSH content and concentration and the weight of testis, seminal vesicles and ventral prostate have been studied at the ages of 30, 60 and 90 days in spontaneously hypertensive rats (SHR) and normotensive control (WKY) rats. In vitro FSH secretion by pituitaries, and the response to orchidectomy and to exogenous administration of either LHRH (1 microgram) or LHRH agonist (0.05, 0.1, 1, and 5 micrograms/kg) were analyzed in 90-day-old SHR and WKY male rats. Ventral prostate weight and FSH plasma levels were determined in other groups of adult male rats castrated and castrated and implanted for 15 days with silastic capsules containing testosterone, dihydrotestosterone or estradiol. Also FSH plasma levels and pituitary FSH concentration were determined at the ages of 30, 60 and 90 days in SHR and WKY female rats. Male SHR showed increased plasma FSH levels and high testicular weight in all the cases, and enhanced testosterone levels in plasma and pituitary FSH content on days 60 and 90. Weight of seminal vesicles and ventral prostate was normal or reduced, depending on the animal age. Adult SHR had increased FSH secretion in vitro, normal response to orchidectomy and did not exhibit FSH increases after LHRH administration. The efficiency of testosterone to stimulate ventral prostate growth and the ability of estradiol to reduce FSH plasma levels were decreased in SHR. Female SHR showed a significant increase in the pituitary content of FSH on day 30 and on proestrus at the ages of days 60 and 90.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of HSV-1 DNA polymerase by ( R)-(1α,2β,3α)-9-[2,3- bis(hydroxymethyl)cyclobutyl]guanine and ( S)-(1α,2β,3α)-9-[2,3- bis(hydroxymethyl)cyclobutyl]guanine

This chapter discusses the polynucleotide polymerization and prostate proliferation. Many enzymes in animal tissues are involved in DNA replication and in the related processes of DNA repair and genetic recombination. The monomeric building blocks are invariably the deoxyribonucleoside triphosphates dATP, dCTP, dGTP, and dTTP. Several characteristics of the replicative DNA polymerase reactions that are greatly increased during the hyperplastic phase of rat ventral prostate growth. The characteristics of reactions as catalyzed by prostate extracts were examined in considerable detail so as to establish optimal assay conditions. It is found that when various adult rat organs were homogenized in dilute thiol-containing buffers and then ultracentrifuged, high D-DNA polymerase activities were observed only with soluble extracts of tissues, such as spleen and testis that contained large numbers of dividing cells. The remarkable difference between the two deoxyribonucleotide polymerizations catalyzed by soluble prostate extracts is that the R-DNA polymerase reaction was much more inhibited by the direct addition of low concentrations of ethidium bromide than was the D-DNA polymerase. It is found that the rat prostate soluble D-DNA and R-DNA polymerase reactions exhibit very different patterns of changes in response to alterations in the androgenic status of the animals.

The Selectivity of a New Progestin

Norgestimate is a new progestin developed for use with ethinyl estradiol as a combination oral contraceptive. It binds to rabbit uterine progestational receptors and in the oral form stimulates a progestational endometrial effect in rabbits. Norgestimate also exerts a direct effect on target organs, stimulating the endometrium in rabbits when injected directly into the uterine horn and inhibiting luteinizing hormone release from rat pituitary cells in culture. Like other progestins, norgestimate inhibits ovulation in several species and estrogen-induced vaginal cornification in ovariectomized rats, but it is not estrogenic. Unlike other progestins, including levonorgestrel and gestodene, norgestimate is relatively free of androgenic activity. Norgestimate's affinity for the androgen receptor is very poor (0.003 x dihydrotestosterone [DHT]), even poorer than that of progesterone (0.005 x DHT). In sharp contrast are the marked affinities of levonorgestrel (0.220 x DHT) and gestodene (0.154 x DHT) for that receptor. The selectivity of norgestimate at receptor level is demonstrated clearly by its highly favorable androgen-to-progestin binding ratio. Norgestimate is similar to progesterone in not significantly stimulating ventral prostate growth in immature rats, whereas levonorgestrel, gestodene, and desogestrel are significantly androgenic in this model. Further evidence of norgestimate's minimal androgenicity is its lack of affinity for human sex hormone binding globulin in vitro. In conclusion, these preclinical studies, consistent with clinical studies, demonstrate the progestational efficacy and selectivity of norgestimate.

Non‐androgenic role of testis in enhancing ventral prostate growth in rats

This study was conducted to investigate whether the testis, aside from its ability to secrete androgen, is able to promote prostatic growth in rats. Increasing quantities of silastic capsules filled with crystalline dihydrotestosterone (DHT) were implanted subcutaneously into adult Sprague-Dawley rats at the time of bilateral epididymo-orchiectomy or sham operation on the testes. Control animals received empty capsules. Twenty-eight days later, the growth of the ventral prostate as measured by wet weight, DNA, and protein content per prostate was significantly greater in rats with intact testes than in orchiectomized rats. An overall increased growth was noted at all doses of exogenous DHT administered. Serum levels of luteinizing hormone in animals treated with DHT were undetectable. Serum levels of testosterone in intact rats treated with DHT were not significantly different from those in castrated rats. These observations suggest a non-androgenic role for the testis and, perhaps, epididymis in promoting prostatic growth in rats, and are consistent with the concept that a non-androgenic substance, produced from the testis and/or epididymis, is able to enhance prostate growth induced by androgen stimulation. The possibility that this phenomenon may play a role in the benign growth of the prostate observed in aging human males with decreased blood levels of androgen warrants consideration.

Androgen metabolism and regulation of rat ventral prostate growth and acid phosphatase during sexual maturation.

Androgen metabolism and the regulation of rat ventral prostate cell proliferation and secretory function were examined during sexual maturation. Changes in acid phosphatase (AP) characteristics were measured as a marker of androgen-dependent prostatic secretory function. In immature (21-day-old) rats, total AP activity per cell was low (14.2 +/- 1.3 mol p-nitrophenol phosphate hydrolysed/h per mg DNA); it increased threefold as the weight, protein and DNA contents of the prostate increased to adult (65-day) levels. This corresponded with significant (P less than 0.001) increases in the staining intensities of three of the four bands of secretory AP on isoelectric focusing gels. The extent of inhibition of AP by tartrate decreased at the same time. Secretory AP is known to be relatively tartrate-resistant. The changes in AP activity occurred after prostatic 5 alpha-dihydrotestosterone (5 alpha-DHT) levels increased from 4.6 +/- 0.7 pmol/mg DNA (21 days) to reach a peak of 17.6 +/- 2.3 pmol/mg DNA at 58 days. Prostatic 5 alpha-DHT concentrations were always higher than testosterone levels. Prostatic 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-Adiol) levels were lower than 5 alpha-DHT levels except on day 58 when levels peaked dramatically at 26.2 +/- 5.5 pmol/mg DNA. Changes in prostatic 5 alpha-DHT and 3 alpha-Adiol levels corresponded with changes in 5 alpha-reductase and 3 alpha-hydroxysteroid oxidoreductase (3 alpha-HSOR) activities. The oxidative reaction of 3 alpha-HSOR was approximately fourfold higher than the reductive reaction, indicating a preference for the formation of 5 alpha-DHT. The plasma levels of testosterone, 5 alpha-DHT and 3 alpha-Adiol cannot account for their respective prostatic levels, indicating the importance of the steroid-metabolizing enzymes in regulating intracellular androgen levels. Changes in the AP characteristics could be correlated with the androgen status of the prostate.

Differential effects of 2-difluoromethylornithine and methylglyoxal bis(guanylhydrazone) on the testosterone-induced growth of ventral prostate and seminal vesicles of castrated rats.

2-Difluoromethylornithine totally prevented any increases in putrescine and spermidine concentrations in the ventral prostate of castrated rats during a 6-day testosterone treatment. Prostatic ornithine decarboxylase activity was inhibited by 80%, whereas S-adenosylmethionine decarboxylase was stimulated by more than 9-fold. In seminal vesicle, the inhibition of putrescine and spermidine accumulation, as well as of ornithine decarboxylase activity, was only minimal, and no stimulation of S-adenosylmethionine decarboxylase was observed. Administration of methylglyoxal bis(guanylhydrazone) to castrated androgen-treated rats resulted in a marked increase in concentrations of all prostatic polyamines. Prostatic ornithine decarboxylase activity was nearly 2 times and adenosylmethionine decarboxylase activity 9 times higher than that of the testosterone-treated animals. In contrast with ventral prostate, methylglyoxal bis(guanylhydrazone) treatment inhibited moderately the accumulation of spermidine and spermine in seminal vesicle, although both ornithine decarboxylase and S-adenosylmethionine decarboxylase activities were stimulated. Difluoromethylornithine inhibited significantly the weight gain of ventral prostate, but methylglyoxal bis(guanylhydrazone) produced a substantial increase in prostatic weight. These changes were largely due to the fact that the volume of prostatic secretion was greatly decreased by difluoromethylornithine, whereas methylglyoxal bis(guanylhydrazone) increased the amount of secretion. Treatment with difluoromethylornithine strikingly increased the methylglyoxal bis(guanylhydrazone) content of both ventral prostate and seminal vesicle, but even under these conditions the drug concentration remained low in comparison with other tissues. The results indicate that a combined use of these two polyamine anti-metabolites does not necessarily result in a synergistic growth inhibition of the androgen-induced growth of male accessory sexual glands.

New progestagens

The profile of norethisterone and newly developed derivatives thereof were assessed by in vitro binding and transactivation assays on progesterone (PR) as well as on androgen (AR) receptors and by subcutaneous treatment in in vivo models. The following in vivo models were performed: A McPhail test for progestational activity in immature rabbits, an ovulation inhibition test in cycling rats and a Hershberger test for androgenic activity in immature orchidectomised rats. The compounds tested were: norethisterone (NET), 11-methylene-NET (11-NET), Δ15-NET (15-NET), 18-methyl-NET (18-NET, Levonorgestrel, LNG), 11-methylene-Δ15-NET (11,15-NET), 11-methylene-18-methyl-NET (11,18-NET, 3-keto-desogestrel, Etonogestrel, ETG), (Δ15-18-methyl-NET (15,18-NET, Gestodene, GSD) and 11-methylene-Δ15-18-methyl-NET (11,15,18-NET). Compared to the non-substituted compound NET, the binding to and agonistic activity via PR was increased for all the three mono-substituted compounds, although the stimulatory effect of 15-NET was only twofold. Compounds with 18-methyl in combination with Δ15 (GSD), with 11-methylene (ETG) or with both combined showed clear synergistic effects, leading to equipotent compounds. If the 18-methyl group was lacking as in 11,15-NET, potency was lower than for ETG or GSD, but higher than for 18-NET (LNG). A correlation coefficient of 0.9 was found between binding affinity and agonistic potency. With respect to the AR binding and transactivation activities, the 18-methyl group potentiated androgenic in vitro activity (LNG). The 11-methylene group increased relative binding affinity in NET, but reduced androgenic activity clearly when also other substituents were present (11,15-NET, ETG and 11,15,18-NET). The Δ15 bond alone did not change the binding in NET, but decreased androgen binding, induced by the 18-methyl substituent, in GSD and 11,15,18-NET. Transactivation activity was also diminished in the compounds having a Δ15 bond. In the McPhail test mono-substitution of NET increased the progestagenic in vivo activity three to five times. Bi- and tri-substitution enhanced the activity further. With respect to ovulation inhibition mono-substitution of NET resulted in three to nine times more potent compounds, whereas bi- and tri-substitution increased potency further, except for 11,15-NET, which was as active as 11-NET. The relative progestagenic potencies in the McPhail and ovulation inhibition tests, correlated significantly with those of the relative binding affinity values (correlation coefficient of 0.91 and 0.93, respectively) and relative transactivation activity values (0.88 and 0.81) for the PR. In the Hershberger test, all the compounds increased androgenic activity with respect to growth of ventral prostate weight compared to NET, with the exception of 11,15-NET and 11,15,18-NET. The androgenic activity was negligible for these latter compounds. The androgenicity of both 18-NET (LNG) and 15,18-NET (GSD), on the other hand, was significantly higher than that of 11,18-NET (ETG). The results of this in vivo test are in line with the AR binding and transactivation activity values (correlation coefficients of 0.86 and 0.88). In addition, selectivity indices were calculated by dividing the progestational potencies by androgenic potencies for both in vitro and in vivo assays. ETG and GSD had clearly higher in vitro and in vivo indices than the other compounds with NET and LNG having the lowest indices. Because the androgenicity of 11,15-NET and 11,15,18-NET was very low, no exact selectivity ratios could be calculated for these compounds. From these experiments we may conclude that small structural modifications exert enhancement of progestational activity and a clear reduction in androgenicity leading to very selective progestagenic compounds. The influence of bi-substitution is additive over mono-substitution, whereas tri-substition is not additive. The three substituents (11-methylene, Δ15 bond and 18-methyl) increase the progestational activity over that of NET and combinations of these substituents result in an even further increase in activity. The effect on androgenic activity of the three substituents is more complex: the 18-methyl group similar as in LNG increases the androgenic activity, whereas the 11-methylene group increases RBA in NET, but reduces androgen binding in combination with any other substituent (ETG, 11,15-NET and 11,15,18-NET). The Δ15 bond had no effect in NET, but decreased androgen binding, induced by the 18-methyl substituent, in GSD and 11,15,18-NET. The effects of these eight progestagens in in vitro binding and transactivation studies are very representative for in vivo endometrium proliferation in rabbits, ovulation inhibition in rats and growth of ventral prostate in orchidectomised rats.

Effect of α-difluoromethylornithine, an enzyme-activated irreversible inhibitor of ornithine decarboxylase, on polyamine levels in rat tissues

α-Difluoromethylornithine (RMI 71.782), an enzyme-activated irreversible inhibitor of ornithine decarboxylase (E.C. 4.1.1.17) in vitro , causes a rapid, long-lasting, dose-dependent decrease of ornithine decarboxylase activity in prostate and, to a lesser extent, in thymus and testis of rats when injected intraperitoneally. Repeated doses (100 mg/kg or 1 g/kg) of α-difluoromethylornithine given to rats for two weeks markedly decreased polyamine concentrations in several rat tissues and selectively slowed down growth of ventral prostate and of thymus.

Does androgen influence prolactin secretion?

In both intact and castrated male and female rats, administration of the A-ring reduced androgen, dihydrotestosterone (DHT), consistently failed to stimulate prolactin (PRL) secretion although it inhibited LH release and, in males, stimulated ventral prostate growth. In intact females, but not in the other types of rat, DHT actually suppressed PRL release. These findings do not support generalizations, based entirely on findings with testosterone, that both "androgens" and estrogens exert stimulatory actions on PRL secretion. The distinct stimulatory effects of testosterone and its esters on PRL secretion seem attributable, not to their androgenic actions per se, but to the ability of testosterone to form estrogenic metabolites. This ability does not appear to be shared by the "pure" androgen, DHT.

A morphological study of the prostatic lobes and the seminal vesicles of castrated rats injected with oestradiol and/or insulin.

The growth of the ventral and dorsolateral prostate, the coagulating glands and the seminal vesicles was studied morphologically in castrated rats following 21 daily injections of oestradiol benzoate or protamine zinc insulin alone or in combination. Oestradiol benzoate was given in daily doses of 0.010 mg, protamine zinc insulin in daily doses of 10 IU. In the ventral and dorsolateral prostate oestradiol had an androgen-like action inducing epithelial growth and secretory activity in the epithelium. In the seminal vesicles and coagulating glands oestradiol induced an increased fibromuscular growth. Protamine zinc insulin induced growth and secretory activity in the dorsolateral prostate, while no such effect was observed in the other accessory reproductive glands. Protamine zinc insulin accentuated the androgen-like action of oestradiol benzoate on the epithelium of the dorsolateral prostate but did not influence on the increased fibromuscular growth seen after oestradiol in the coagulating glands and the seminal vesicles.

Polynucleotide Polymerizations and Prostate Proliferation

Publisher Summary This chapter discusses the polynucleotide polymerization and prostate proliferation. Many enzymes in animal tissues are involved in DNA replication and in the related processes of DNA repair and genetic recombination. The monomeric building blocks are invariably the deoxyribonucleoside triphosphates dATP, dCTP, dGTP, and dTTP. Several characteristics of the replicative DNA polymerase reactions that are greatly increased during the hyperplastic phase of rat ventral prostate growth. The characteristics of reactions as catalyzed by prostate extracts were examined in considerable detail so as to establish optimal assay conditions. It is found that when various adult rat organs were homogenized in dilute thiol-containing buffers and then ultracentrifuged, high D-DNA polymerase activities were observed only with soluble extracts of tissues, such as spleen and testis that contained large numbers of dividing cells. The remarkable difference between the two deoxyribonucleotide polymerizations catalyzed by soluble prostate extracts is that the R-DNA polymerase reaction was much more inhibited by the direct addition of low concentrations of ethidium bromide than was the D-DNA polymerase. It is found that the rat prostate soluble D-DNA and R-DNA polymerase reactions exhibit very different patterns of changes in response to alterations in the androgenic status of the animals.