Development of a vagina in male rats by inhibiting androgen receptors with an anti-androgen during the critical phase of organogenesis

Targeting the relaxin hormonal pathway in prostate cancer

Targeting the androgen signalling pathway has long been the hallmark of anti-hormonal therapy for prostate cancer. However, development of androgen-independent prostate cancer is an inevitable outcome to therapies targeting this pathway, in part, owing to the shift from cancer dependence on androgen signalling for growth in favor of augmentation of other cellular pathways that provide proliferation-, survival- and angiogenesis-promoting signals. This review focuses on the role of the hormone relaxin in the development and progression of prostate cancer, prior to and after the onset of androgen independence, as well as its role in cancers of other reproductive tissues. As the body of literature expands, examining relaxin expression in cancerous tissues and its role in a growing number of in vitro and in vivo cancer models, our understanding of the important involvement of this hormone in cancer biology is becoming clearer. Specifically, the pleiotropic functions of relaxin affecting cell growth, angiogenesis, blood flow, cell migration and extracellular matrix remodeling are examined in the context of cancer progression. The interactions and intercepts of the intracellular signalling pathways of relaxin with the androgen pathway are explored in the context of progression of castration-resistant and androgen-independent prostate cancers. We provide an overview of current anti-hormonal therapeutic treatment options for prostate cancer and delve into therapeutic approaches and development of agents aimed at specifically antagonizing relaxin signalling to curb tumor growth. We also discuss the rationale and challenges utilizing such agents as novel anti-hormonals in the clinic, and their potential to supplement current therapeutic modalities.

Exogenous androgen during development alters adult partner preference and mating behavior in gonadally intact male rats

In the rat, neonatal administration of testosterone propionate to a castrated male causes masculinization of behavior. However, if an intact male is treated neonatally with testosterone (hyper-androgen condition), male sexual behavior in adulthood is disrupted. There is a possibility that the hyper-androgen treatment is suppressing male sexual behavior by altering the male's partner preference and thereby reducing his motivation to approach the female. If so, this would suggest that exposure to supra-physiological levels of androgen during development may result in the development of male-oriented partner preference in the male. To test this idea, male rats were treated either postnatally or prenatally with testosterone, and partner preference and sexual behavior were examined in adulthood. The principal finding of this study was that increased levels of testosterone during early postnatal life, but not prenatal, decreased male sexual behavior and increased the amount of time a male spent with a stimulus male, without affecting the amount of time spent with a stimulus female during partner preference tests. Thus, the reduction in male sexual behavior produced by early exposure to high levels of testosterone is not likely due to a reduction in the male's motivation to approach a receptive female.

The OECD program to validate the rat Hershberger bioassay to screen compounds for in vivo androgen and antiandrogen responses. Phase 1: use of a potent agonist and a potent antagonist to test the standardized protocol

The Organisation for Economic Cooperation and Development (OECD) has completed phase 1 of the Hershberger validation intended to identify in vivo activity of suspected androgens and antiandrogens. Seventeen laboratories from 7 countries participated in phase 1, and results were collated and evaluated by the OECD with the support of an international committee of experts. Five androgen-responsive tissues (ventral prostate, paired seminal vesicles and coagulating glands, levator ani and bulbocavernosus muscles, glans penis, and paired Cowper's or bulbourethral glands) were evaluated. The standardized protocols used selected doses of a reference androgen, testosterone propionate (TP), and an antiandrogen, flutamide (FLU). All laboratories successfully detected TP-stimulated increases in androgen-responsive tissue weight and decreases in TP-stimulated tissue weights when FLU was co-administered. The standardized protocols performed well under a variety of conditions (e.g., strain, diet, housing protocol, bedding). There was good agreement among laboratories with regard to the TP doses inducing significant increases in tissue weights and the FLU doses decreasing TP-stimulated tissue weights. Several additional procedures (e.g., weighing of the dorsolateral prostate and fixation of tissues before weighing) and serum component measurements (e.g., luteinizing hormone) were also included by some laboratories to assess their potential utility. The results indicated that the OECD Hershberger protocol was robust, reproducible, and transferable across laboratories. Based on this phase 1 validation study, the protocols have been refined, and the next phase of the OECD validation program will test the protocol with selected doses of weak androgen agonists, androgen antagonists, a 5alpha-reductase inhibitor, and chemicals having no androgenic activity.

Conception and pharmacodynamic profile of drospirenone

Progesterone is more than a progestin. Beyond functions in cycle and pregnancy, progesterone binds with high affinity to the mineralocorticoid receptor (MR) acting as an antagonist, with obvious significance for electrolyte homeostasis, an array of MR-related functions in the circulation as well as in the CNS. Progesterone induces natriuresis at physiological concentrations. Lack of antimineralocorticoid activity with conventional progestins may account for sodium and water retention, minor elevation of blood pressure and "pill hypertension" in susceptible women on oral contraceptives. Ethinylestradiol (EE) contributes to this problem by distinct activation of the renin-angiotensin-aldosterone (RAAS) system. Drospirenone (DRSP: 6beta,7beta,15beta,16beta-dimethylene-3-oxo 17alpha-pregn-4-ene-21,17 carbolactone) is the first synthetic progestin with antialdosterone activity. DRSP and progesterone bind to PR in uterine (affinity of both is about 30% of R5020) and MR in kidney cytosol (affinity about 230 and 100% of aldosterone, respectively). Intrauterine administration of DRSP in silastic tubes induced maximum local progestational effects in rabbits. At systemic subcutaneous (s.c.) administration (McPhail-assay) full endometrial transformation was obtained at 1mg per animal per day. At 1-3mg DRSP per animal per day subcutaneously, pregnancy maintenance after ovariectomy, antiovulatory activity, and antimineralocorticoid activity were seen in the respective assays in rats. The latter activity indicates about eight-fold higher potency than spironolactone. DRSP decreased blood pressure in male hypertensive rats, whereas an increase was noted under conventional progestins. DRSP also prevented hypertension and fetal growth retardation in pregnant rats after L-NAME, an inhibitor of nitric oxide synthase. DRSP has antiandrogenic activity. Feminizing effects were recorded during sexual differentiation in male fetuses at high doses. Powerful antiandrogenic effects were also seen in gonad intact and testosterone substituted castrated male rats. The antiandrogenic potency of DRSP is superior to that of spironolactone but below that of cyproterone acetate. Endometrial transformation, inhibition of ovulation, and antimineralocorticoid, i.e. natriuretic effects and mild antiandrogenic effects were recorded at the same range of oral doses (0.5-4 mg per day) in humans. Combined with EE (3 mg DRSP+30 microg EE), DRSP provides effective inhibition of ovulation and cycle control. Body weight compared to conventional oral contraceptives was reduced. DRSP (3 mg per day+15, 20, or 30 microg ethinyl estradiol per day) prevented the mild increase of blood pressure seen under a conventional levonorgestrel-containing contraceptive and even tended to reduce pretreatment blood pressure. Studies on modulation (i.e. inhibition) of glucocorticoid effects at the MR in the CNS remain an unexplored and interesting area for research.

The effect of androgen deprivation on branching morphogenesis in the mouse prostate

Androgen-induced prostatic development encompasses many individual processes such as ductal branching morphogenesis, cellular proliferation, and secretory cytodifferentiation. Previous studies of ductal morphogenesis (Y. Sugimura, G.R. Cunha, and A.A. Donjacour, 1986, Biol. Reprod. 34, 961-971) demonstrated that the majority (approximately 70%) of ductal tips and branchpoints in the mouse prostate is generated before 15 days of age. Since circulating androgen levels are low during this neonatal period, it is possible that ductal branching morphogenesis may not require the continuous presence of androgens. To test this hypothesis mice were castrated within 24 hr of birth, and prostates from these mice were microdissected at various ages from 5 to 120 days of age to assess the number of ductal tips and branchpoints; wet weight and DNA content were also determined. In intact males wet weight and DNA content increased rapidly between 15 and 60 days of age, after most of the prostatic ductal architecture had been laid down. Neonatal castration considerably reduced the number of tips and branchpoints in both the ventral and dorsolateral prostate, yet both lobes still underwent significant branching morphogenesis in the absence of testes. The administration of anti-androgens to neonatal castrates did not suppress ductal branching to any greater extent than did neonatal castration alone. Androgen replacement immediately following neonatal castration resulted in precocious attainment of the adult number of tips and branchpoints, but caused only modest increases in wet weight. In contrast, when androgen replacement was delayed until adulthood, prostatic wet weight increased to normal adult levels, but the number of ductal tips and branchpoints did not. These experiments show that neonatal prostatic ductal morphogenesis is sensitive to, but does not require, chronic androgen stimulation.

Induction of Müllerian duct derivatives in testicular feminized (Tfm) mice by prenatal exposure to diethylstilbestrol

When pregnant mice carrying the Tfm mutation gene were injected with diethylstilbestrol (DES) from Days 9 to 16 of gestation, the regression of the Müllerian duct derivatives was inhibited in their wild male and Tfm male offspring. The degree of persistence of the Müllerian duct derivatives demonstrated a dependence on DES dose. Complete or almost complete preservation of the Müllerian ducts was observed in the animals exposed to high doses of DES. Since Tfm males from non-injected mothers had no reproductive tract except the vaginal anlage, despite the presence of testes, bilateral occurrence of the Müllerian duct derivatives in Tfm males following prenatal exposure to DES indicates that the characteristic features of the reproductive tract in these animals are almost the same as that in normal females.

Testicular Changes in the Rat by Prepuberal Administration of a Synthetic Antiandrogen

The testes of treated animals showed mature spermatozoa and a smaller surface of tubules. Spermatic wave shifted, showing more mitotic figures and less mature spermatozoa. Antiandrogen plus testosterone propionate (TP) and human chorionic gonadotropin (hCG) administration showed, respectively, increased and decreased prostate and testicular weights. Histological aspects of the tubules did not improve by hormonal replacement; instead, altered and multinucleated cells appeared. Testicular modifications showed that antiandrogen administration induced changes in gonadotropin secretion.

Induction of estrogen-independent persistent vaginal cornification in cyproterone acetate (CA)-induced feminized male mice

Pregnant ICR/JCL mice were treated with 6 mg of cyproterone acetate (CA) from days 14 to 20 of pregnancy to feminize male offspring. Feminized males delivered on day 20 of pregnancy by cesarean section were castrated the same day, injected with estradiol-17beta(E2) or sesame oil from the day of delivery (=day 1) to day 10 and sacrificed on day 60. In oil-injected feminized males, the vaginal epithelium was atrophic and did not show cornification. In feminized males given 20 microgram E2 neonatally, the vaginal epithelium exhibited well-differentiated stratified squamous organization, but was not cornified in seven out of the nine mice of this group. In the mice treated with 50 microgram E2, persistent cornification was recognized most frequently in the posterior two-thirds of the vaginal epithelium which is considered to originate from the urogenital sinus. However, the incidence of cornification in the anterior one-third which may contain the epithelial cells of müllerian duct was low. These results provide supporting evidence for the possible participation of epithelial cells which come from the urogenital sinus in the development of estrogen-independent persistent vaginal cornification in neonatally estrogenized mice.

The onset of testicular differentiation in the rat: An ultrastructural study

The structure of developing rat testes was studied by light and electron microscopy. Ultrastructural differentiation of Sertoli and Leydig cells was followed from 14 days of gestation through birth. Specialized morphology in Sertoli cells was first seen at 16 days of gestation. In these cells the rough endoplasmic reticulum increased and became organized as numerous short cisternae loaded with a homogenous material. Typical Leydig cells were found among the stromal cells, around day 17 of gestation. There is good correlation between the time of appearance of ultrastructural specialization and published data on secretory capacity of the fetal testes, in respect to the inhibition and differentiation of the Müllerian and Wolffian ducts.

Androgen accumulation andbinding to macromolecules in seminal vesicles: inhibition cyproterone

Cyproterone reduces the accumulation of testosterone and dihydrotestosterone in seminal vesicles 30 minutes after intravenous administration of tritiated testosterone to castrated rats. Testosterone, added in vitro, binds to macromolecules from the supernatant fraction of the seminal vesicle homogenates; this interaction is antagonized competitively by cyproterone. Cyproterone may diminish androgenic effects by competition for binding molecules.