Alpha-dihydrotestosterone Propionate Research Articles

FR146687, a novel steroid 5 alpha-reductase inhibitor: in vitro and in vivo effects on prostates.

Steroid 5 alpha-reductase is implicated in the pathogenesis of benign prostatic hyperplasia (BPH). We studied the in vitro and in vivo effects of FR146687, a new inhibitor of 5 alpha-reductase. Two isozymes of rat and human 5 alpha-reductases were expressed in 293 cells. In vivo effects of drugs were evaluated on rat and dog prostates. Castrated immature rats were injected with testosterone propionate (TP) or 5 alpha-dihydrotestosterone propionate (DHTP) to induce growth of the ventral prostates. Testosterone and 5 alpha-dihydrotestosterone (DHT) contents in rat and dog prostates were measured by gas chromatography-mass spectrophotometry (GC-MS). FR146687 showed noncompetitive inhibition in both isozymes and no inhibitory effects on other steroid oxidoreductases. In mature rats and castrated immature rats treated with TP, FR146687 dose-dependently reduced ventral prostate and seminal vesicle weight at doses above 0.1 mg/kg, while castrated immature rats treated with DHTP were not affected by FR146687. FR146687 showed more potent reduction of rat prostates than finasteride. DHT concentration in the prostates was significantly reduced when FR146687 was administered to rats and beagles. FR146687 is a dual inhibitor for 5 alpha-reductase isozymes and significantly reduced the growth and DHT content in the prostate.

Minimal effects of 17 beta-hydroxy-17 alpha-methyl-estra-4,9,11-triene-3-one (R1881) on sexual behaviour in prepubertally castrated rams.

Ten adult prepubertally castrated rams were injected with 5 alpha-dihydrotestosterone propionate (DHTP; 20 mg/day) for 3 weeks to stimulate genital development. Thereafter, half of the sheep were injected with testosterone (100 mg/day) for a further 4 weeks, while the remainder received the same dose of 17 beta-hydroxy-17 alpha-methyl-estra-4,9,11-triene-3-one (methyltrienolone; R1881). All the animals were tested for sexual behaviour on 15 occasions with ovariectomized ewes in which oestrous behaviour was induced by injections of 50 micrograms oestradiol-17 beta benzoate at 4- to 5-day intervals. Behavioural tests were of 10 min duration and were carried out thrice weekly over a 5-week period, starting in the final week of DHTP treatment. Animals treated with testosterone showed a highly significant increase in courtship behaviour (tongue-flicks; lunges and nudges) after only four daily injections and this level of activity was maintained to the end of the experiment. However, the incidence of courtship activity in sheep treated with R1881 was similar to that recorded during the period of DHTP treatment. All animals given testosterone displayed mounts with pelvic thrusts and erections, and achieved intromission with ejaculation. These activities remained significantly more frequent than in sheep treated with R1881, starting from tests 9, 8 and 12 respectively. Four of the five individuals in the group given R1881 showed occasional mounts with thrusts, three showed sporadic erections and one sheep intromitted in the final test. These results indicate that, in contrast to the rat, R1881 has only very weak effects on sexual behaviour in the castrated ram.

Age-, Sex-, and Gonadal Steroid-Related Changes in Immunoreactive Substance P in the Rat Anterior Pituitary Gland

The interrelationship of anterior pituitary lobe (AP) immunoreactive substance P (I-SP) concentrations with age, sex, gonadal steroids, and estrous cyclicity in rats was examined. There was no difference between male and female AP I-SP levels at 0.5 month of age. At 2.0 and 5.0 months of age, a sex-linked difference in AP I-SP concentrations was evident, inasmuch as male APs contained approximately 3 and 8 times greater concentrations of I-SP, respectively, than APs from age-matched females. Long term (6 weeks) gonadectomy of adult rats resulted in an increase in I-SP concentrations in female APs and a decrease in the concentrations of the peptide in male APs compared to values in their respective sham-operated controls. Treatment of gonadectomized animals for the same length of time with gonadal steroid-filled Silastic capsule implants resulted in qualitatively identical responses in males and females; that is, estradiol benzoate decreased and 5 alpha-dihydrotestosterone propionate increased AP I-SP levels compared to the respective control values in castrates. Testosterone propionate treatment had no effect on AP I-SP levels compared with the respective gonadectomy control values. Short term (8 days) gonadectomy of adult males did not affect the AP concentration of I-SP. Likewise, gonadectomy of adult females was ineffective in altering the AP I-SP concentration compared with concentrations in females on diestrous day 1, diestrous day 2, proestrous, or estrous stages of the vaginal cycle. These data suggest that gonadal steroids are physiologically important in the regulation of I-SP concentrations in the AP. We hypothesize that I-SP is indigenous to the AP and that gonadal steroids act directly at the level of the AP to affect the synthesis and/or release of the peptide.

The passage of 5 alpha-dihydrotestosterone from serum into cerebrospinal fluid and LH negative feedback in castrated rhesus monkeys.

Seven castrated monkeys were given either 50 or 100 micrograms 5 alpha-dihydrotestosterone (DHT) propionate/kg per day. There was no correlation between serum and cerebrospinal fluid (CSF) levels of DHT, which remained very low in the CSF (0.3-0.6% of blood levels) despite the presence of high, supraphysiological amounts in the circulation. There was also no relation between unbound DHT in the blood and the CSF, in which all DHT is unbound. These results differ from previous work on testosterone, the metabolic precursor of DHT. 5 alpha-Dihydrotestosterone propionate at the higher dose maintained suppressed levels of serum LH; LH in two out of four monkeys treated at the lower dose increased to levels observed in castrated, untreated rhesus monkeys. There was no predictable relationship between the amount of DHT in the CSF and levels of LH in the blood: by contrast, DHT in the blood was correlated with serum levels of LH. Levels of LH rose in monkeys in which total blood DHT fell below about 68 nmol/l and, even more obviously, if unbound DHT decreased to less than about 2 nmol/l. Differences between the distribution of testosterone and DHT between blood and CSF cannot be explained by serum binding, lipid solubility or clearance from the brain, and suggest that there may be some mechanism for excluding DHT from the CSF. Though DHT reaches the CSF from the blood in small amounts, levels there do not relate predictably to those in the vascular compartment. It seems unlikely, therefore, that levels of intracerebral DHT are controlled by changes in those of the blood.

Behavioural and morphological effects of 5 alpha-dihydrotestosterone and oestradiol-17 beta in the prepubertally castrated boar.

Three groups of 5 prepubertally castrated boars received twice weekly subcutaneous injections from 16 to 28 weeks of age of 5 alpha-dihydrotestosterone propionate (1 mg/kg), oestradiol-17 beta dipropionate (0.1 mg/kg), or a combination of the two steroids. The pigs were tested each week for sexual behaviour with an oestrogen-treated ovariectomized gilt. 5 alpha-Dihydrotestosterone did not induce copulatory behaviour whereas oestradiol initiated mounting, although this behaviour was not maintained. However, the combined hormonal treatment induced the full pattern of copulation, including ejaculation, in 4/5 pigs. Oestrogen-treated animals also showed champing and salivation. None of the pigs treated with 5 alpha-dihydrotestosterone showed lordosis when exposed to a mature boar. Increases in the size of the penis, the ischio- and bulbocavernosus muscles, seminal vesicles and bulbourethral glands were produced by 5 alpha-dihydrotestosterone, and, with the exception of the penis, this hypertrophy was further enhanced by additional treatment with oestradiol. Increases in the weight of the prostate and muscular urethra were due mainly to the effects of oestrogen; this steroid caused extensive development of fibromuscular tissue and also increased mammary teat length. In the submaxillary salivary glands, synergism between 5 alpha-dihydrotestosterone and oestradiol resulted in hypertrophy of the serous cells.

Dihydrotestosterone-induced inhibition of lordosis in estrogen-primed ovariectomized rats following 6-hydroxydopamine or electrolytic septal lesions

The dose-dependent inhibition of lordosis by 5 alpha-dihydrotestosterone propionate in ovariectomized female rats treated concurrently with estradiol benzoate was attenuated neither by intracranial 6-hydroxydopamine injections which reduced dopamine concentrations by approximately 70% in septum or 75% in both septum and n. accumbens septi nor by electrolytic destruction of the lateral or medial septal nuclei or of both septal nuclei. These results suggest that inhibitory effect of dihydrotestosterone on estrogen-induced lordosis does not critically depend on the mesolimbic dopaminergic innervation of the forebrain or on the septal nuclei.

Pituitary receptor sites for gonadotropin-releasing hormone: effect of castration and substitutive therapy with sex steroids in the male rat.

To examine the role of pituitary gonadotropin-releasing hormone (GnRH) receptors (pit GnRH-R) in the regulation of gonadotropin secretion, male rats were orchidectomized and then selectively received substitutive therapy with sex steroids. Pituitary content of GnRH-R was determined by saturation analysis, using radioiodinated [D-Trp6,(N-Et)Pro5,des-Gly10]GnRH as tracer. Castration produced a rapid and sustained increase of the number of GnRH-R, which doubled after 2 days, and after 10 days the pituitary content of GnRH-R was 258 +/- 23 fmol/pituitary compared to 103 +/- 12 fmol/pituitary for sham-operated control animals. No change of the affinity constant (Ka) was observed (Ka = 1.13 +/- 0.08 X 10(10) M-1; n = 14). Plasma LH increased 5- to 10-fold and FSH-2- to 3-fold after castration, and hypothalamic GnRH content was depleted by 30-60%. Immediate substitution of castrated rats with testosterone propionate (250 micrograms daily) prevented the increases of both plasma gonadotropins and of GnRH-R. Treatment of acutely castrated rats for 7 days with testosterone propionate (50-200 micrograms), 5 alpha-dihydrotestosterone propionate (25-400 micrograms), or estradiol benzoate (2 micrograms) prevented the rise in pit GnRH-R in a dose-related manner and normalized the other parameters studied except that plasma FSH remained slightly elevated. In contrast, when substitutive therapy was started 8 days after castration or later, the 7-day treatment with sex steroids reduced plasma gonadotropins, but pit GnRH-R remained elevated, and hypothalamic GnRH content remained depleted. These results indicate that the marked increase of gonadotropin secretion after castration is mediated at least in part, by an increase in the number of pit GnRH-R. Sex steroids were able to reverse all castration-induced endocrine changes in acutely castrated rats, but in long term castrated animals their action at higher centers to normalize hypothalamic GnRH content, and indirectly, to reduce pit GnRH-R content, was either delayed or ineffective. Thus, the rapid feedback action of sex steroids in long term castrated rats may be predominantly exerted at the pituitary level.

Attenuation by a 5 alpha-reductase inhibitor of the activational effect of testosterone propionate on penile erections in castrated male rats.

Daily administration of an inhibitor of 5 alpha-reductase, 17 beta-testosterone carboxylic acid, significantly attenuated the stimulatory effect of testosterone propionate on penile erections displayed by castrated male rats which were restrained in a supine position. This treatment, however, failed to affect mating behavior in tests with sexually receptive females. The inhibitory effect of 17 beta-testosterone carboxylic acid on erection was reversed by concurrent administration of 5 alpha-dihydrotestosterone propionate, suggesting that the 5 alpha-reduced metabolite(s) of testosterone may normally contribute to the activation of penile erection in the rat.

Effects of androgens on dietary self-selection and carcass composition in male rats.

The aromatizable androgen testosterone propionate (TP; .2 mg/day) increased protein and carbohydrate intake and stimulated body weight gain in gonadectomized (Gdx) male rats. A higher dose of TP (2.0 mg/day) increased protein, but not carbohydrate, intake and was less effective in stimulating body weight gain than the lower dose of TP. Postmortem carcass analyses revealed that the elevated protein intake of both TP-tested groups was associated with increased carcass protein content. The decreased weight of rats treated with the high dose of TP was due to a reduction in body fat content. The nonaromatizable androgen 5 alpha-dihydrotestosterone propionate (DHTP; .2 or 2.0 mg/day) also increased protein (but not carbohydrate) intake and body weight gain in Gdx male rats, but it did not alter carcass composition. Unlike TP, the two doses of DHTP were equally effective, but neither dose of DHTP was as effective as the low dose of TP in stimulating protein and carbohydrate intake and body weight gain. The results of these experiments suggest that (a) androgens can increase selection of dietary protein whether or not they exert significant protein anabolic effects, (b) the 5 alpha-reduced product of testosterone, 5 alpha-dihydrotestosterone, is not the major metabolite responsible for the increases in protein and caloric intake and in body weight caused by TP, and (c) the decreases in carbohydrate intake and adiposity in rats treated with the high dose of TP may be mediated by aromatized (estrogenic) metabolites of the androgen.

Occurrence of permanent changes in vaginal and uterine epithelia in mice treated neonatally with progestin, estrogen and aromatizable or non-aromatizable androgens.

Female mice of the C57 Black/Tw strain were injected daily with 100 microng testosterone, 50 microng testosterone propionate (TP), 100 microng 5 alpha-dihydrotestosterone (DHT) or 50 microng 5 alpha-dihydrotestosterone propionate (DHTP), for 10 days from the day of birth. Two other groups of female mice were given neonatal injections with 20 microng estradiol-17 beta and 100 microng progesterone for 10 days, respectively. All mice were ovariectomized at 60 days of age and killed at 90 days. In 100% of neonatally estrogenized or androgenized, ovariectomized mice, the cranial part of the vagina was lined with stratified epithelium with either cornification or parakeratosis or mucification. Stratification only or stratification with superficial squamous metaplasia or cornification took place in the uterine epithelia of 18% of the TP-treated, 75% of the DHT-treated and 50% of the DHTP-treated, ovariectomized mice. In contrast, neonatally estrogenized, ovariectomized mice did not show the estrogen-independent, persistent uterine changes. Neonatal progesterone treatment failed to induce the permanent changes in the vaginal and uterine epithelia.

Effects of testosterone propionate or dihydrotestosterone propionate on plasma FSH and LH levels in neonatal rats and on sexual differentiation of the brain.

The present study tests the hypothesis that the effects of perinatal androgen administration on the development of the brain are brought about indirectly by a suppression of plasma gonadotropin (GTH) titers. Both castrated male and intact female rats were treated neonatally with 5 alpha-dihydrotestosterone propionate (DHTP) or testosterone propionate (TP) throughout the first ten postnatal days of life and the corresponding effects on neonatal plasma FSH and LH levels and the subsequent ability of the adult to exhibit cyclic GTH release and female sex behavior (lordosis) were determined. In males castrated within 24 h of birth, subcutaneous injections of DHTP (60 or 180 mug per 100 g average body weight) or TP (60 mug/100 g) given on day 2, 4, 6, 8 and 10 reduced plasma levels of FSH and LH as determined by radioimmunoassay 48 h following the first and last injections. However, TP but not DHTP masculinized the development of the regulation of GTH release as mesured by luteinization of subcutaneous ovarian grafts, and also suppressed the ability of adult neonatally castrated male primed with estradiol benzoate and progesterone to display lordosis behavior. In intact females, the same neonatal DHTP and TP injection regime lowered FSH and LH plasma levels following the last injection (day 12), while DHTP lowered LH, but not FSH, following the first injection (day 4). All TP treated females had ovaries devoid of CL by 45 days of age and showed prolonged vaginal cornification. However, DHTP failed to masculinize the pattern of GTH release in females since DHTP-treated females, like oil-treated females, possessed CL(days 45 and 100) and exhibited vaginal cycles (days 80-100). Lordosis quotients of females treated neonatally with DHTP were as high as those of oil-treated females and significantly higher than those of TP-treated females. These results demonstrate that the ability of TP to induce maculine differentiation of the neural regulation of GTH release and female sex behavior does not depend on its ability to depress circulating LH and FSH levels in the neonatal male, or LH levels in the neonatal female rat.