Effect of alcohol on the content of sex steroid receptors in the hypothalamus and hypophysis of male rats

In experimental dipsomania model (formation of physical dependence by method of intensive alcoholization) we have studied receptor binding of testosterone (T) and estradiol (E2) in the hypothalamus and pituitary body of mature male rats. Administration (at 10 and 16 h) of 25% ethanol-saline solution at a dose of 7.5 g/kg of body weight in the course of 5 days significantly decreased serum T level but did not change serum LH and FSH levels. Essential reduction of the nuclear androgen receptors in the preoptic-anterior hypothalamic area (POA), mediobasal hypothalamus (MBH) and adenohypophysis was noted in alcohol-treated rats. Unlike androgen receptors the number of the nuclear E2-binding sites in PaO was significantly increased in these males. Thus the results of the present paper demonstrate that multiple administration of ethanol stipulates deficit of serum T, androgen receptors in MBH and pituitary body that possibly results in separation of negative feedback mechanism between the gonads and pituitary body. Increase of specific binding of E2 to nuclear receptors in PoA might appear to explain feminization of alcohol-treated rats.     

Effect of acupuncture on the catecholamine content in the hypothalamus and brain stem of rats with an experimental stomach ulcer

Significant increase of dopamine (DA) in hypothalamus and epinephrine (E) in the brain stem were revealed in the experiment on rats with experimental gastric ulcer (EGU). An acupuncture (AP) session produces a prominent increase in DOPA and especially DA in hypothalamus of the rat with EGU. Under the same conditions A, DOPA and DA in the brain stem increased as compared to the control. It is assumed that acupuncture produces a correcting effect on the reconstructive processes of catecholaminergic systems of the brain occurring in visceral pathology.     

Study of the hypothalamus of neonatally castrated rats by the karyometric method]

The sensitivity of different hypothalamic regions to the effect of androgens has been studied during the period of the brain sex differentiation. The castration of animals during the first week of life was shown to result in the marked increase of size of the neuron nuclei in the preoptic, suprachiasmatic, arcuate and ventromedial nuclei of the hypothalamus; the size of neuron nuclei in the dorsomedial nucleus suffered no changes. The dynamics of size of the cell nuclei was followed in different hypothalamic regions with respect to the time of castration.     

Deciduomal response in androgenized rats: effect of age and steroid replacement therapy

Deciduomal response was studied in female rats androgenized with a single injection of 1 mg of testosterone propionate at 5 days of age. Endometrial scratching in immature rats (33 days) elicited a better response in androgenized rats (AF) than in controls (NF) following induction of ovulation or steroid replacement therapy. In adult females receiving cervical stimulation at estrus or induction of ovulation, strong deciduomal response was obtained in NF rats and no response was observed in AF rats. In ovariectomized (OVX) rats receiving 2 mg of progesterone (P), the response in AF was only 50% that of NF rats. Addition of 0.1 mg of estradiol (E2) enhanced the decidualization in NF rats but completely abolished that of AF rats. Following ovariectomy and a period of 12-15 days without any exogenous hormone, an E2 priming treatment (0.2 or 0.5 micrograms) for 3 days followed by a replacement therapy (2.0 mg P + 0.1 or 0.15 micrograms E2) allowed good response in NF rats. The response was reduced by 30-35% in AF rats receiving 0.1 micrograms of E2 during the replacement therapy and by 66% in AF rats receiving 0.15 micrograms of E2. These results indicate that in AF rats the reduction of the response is age dependent, the uterus is more sensitive to E2 than is the uterus of NF rats and the growth response is always submaximal.     

Action of endogenous steroid inhibitors of brain aromatase relative to fadrozole

To study mechanisms of aromatase inhibition in brain cells, a highly effective non-steroidal aromatase inhibitor (Fadrozole; 4-[5,6,7,8-tetra-hydroimidazo-(1,5-a)-pyridin-5-yl] benzonitrile HCl; CGS 16949A) was compared with endogenous C-19 steroids, known to be formed in the preoptic area, which inhibit oestrogen formation. Using a sensitive in vitro tritiated water assay for aromatase activity in avian (dove) preoptic tissue, the order of potency, with testosterone as substrate was: Fadrozole (K_i < 1 × 10⁻⁹ M) > 4-androstenedione 5-androstanedione > 5-dihydrotestosterone (K_i = 6 × 10⁻⁸ M) > 5β-androstanedione > 5β-dihydrotestosterone (K_i = 3.5 × 10⁻⁷ M) > 5-androstane-3, 17β-diol (K_i = 5 × 10⁻⁶ M) > 5β-androstane-3β,17β-diol. Five other steroids, 5β-androstane-3,17β-diol, 5-androstane-3β,17β-diol, progesterone, oestradiol and oestrone, showed no inhibition at 10⁻⁴ M. The kinetics indicate that endogenous C-19 steroids show similar competitive inhibition of the aromatase as Fadrozole. Mouse (BALB/c) preoptic aromatase was also inhibited by Fadrozole. We conclude that endogenous C-19 metabolites of testosterone are effective inhibitors of the brain aromatase, and suggest that they bind competitively at the same active site as Fadrozole.     

The state of gametes and the type of maturation of follicular oocytes in rats neonatally androgenized by LH-RH-induced ovulation

The character of follicular oocyte maturation and the state of gametes in androgenized rats was studied after LH-RH stimulation. The induction of ovulation with LH-RH has been shown to increase the number of rats with nonovulatory follicules and reduce the number of oocytes maturing prior to the onset of metaphase II. After the induction of ovulation the rate of chromosomal aberrations became higher than in intact animals. Ovulated oocyte population was characterized by the increased number of degenerated gametes. This increase was paralleled by decreased incidence of chromosomal aberrations in ovulated cells.     

Effect of streptozotocin administration on somatostatin content of pancreas and hypothalamus in rats.

A radioimmunoassay (RIA) method for somatostatin (SRIF) utilizing rabbit antiserum against synthetic SRIF coupled with human serum alpha-globulin is described. Synthetic N alpha-tyrosylated SRIF was labelled with 125I using the lactoperoxidase method and purified on a Sephadex G-10 column. This assay system was highly specific for SRIF and did not cross-react with hypothalamic trophic hormones, pituitary trophic hormones or gastrointestinal hormones. The effect of streptozotocin induced diabetes on the SRIF content was examined in the pancreas, the pancreatic islets, as well as the hypothalamus of rats. SRIF content in both the pancreas and islets of the diabetic rats was shown by RIA to have significantly increased. However, content in the hypothalamus of the diabetic rats did not differ from that of the control. The physiological and pathophysiological significance of the SRIF changes remains to determined.     

Effect of beta-endorphin on catecholamine levels in the rat hypothalamus and cerebral cortex

The present paper deals with the effect of beta-endorphin on catecholamine content in the hypothalamus and cerebral cortex of male rats. beta-endorphin was found to decrease catecholamine content in the rat brain, with the degree of reduction depending on the brain topography and the time following the peptide administration. 5 min later no changes in catecholamine content were observed either in the hypothalamus or in the cerebral cortex. 20 min later beta-endorphin induced a statistically significant fall of catecholamine concentration in the hypothalamus. A tendency towards its decrease was also observed in the cerebral cortex. 60 min later beta-endorphin produced an insignificant decrease in catecholamine level in both brain areas under study. It may be therefore suggested that beta-endorphin-induced decrease of catecholamine content in the hypothalamus and cerebral cortex represents one of the mechanisms underlying beta-endorphin stimulating action on a number of trophic functions of the hypophysis.     

Effect of the aromatase inhibitor, 4 hydroxyandrostenedione, on the endotoxin-induced changes in steroid hormones in male rats.

The increase in circulating estrogen concentrations that follows injection of Escherichia coli endotoxin (Endo) may be due to increased aromatase activity. We have therefore analysed the effect of the aromatase inhibitor, 4 hydroxyandrostenedione (4OHA) on the steroid hormone response of male rats, particularly the dramatic increase in estrogens and decrease in androgens, induced by Endo. The concentrations of corticosterone (B), progesterone (P4), 17 alpha hydroxyprogesterone (17 alpha OHP4), androstenedione (delta 4), testosterone (T), estrone (E1) and estradiol (E2) were determined 2 hours after injection of increasing doses of 4OHA with and without Endo. The increase in serum estrogen concentrations and drop in serum androgen levels in response to Endo were blocked by a single dose of 4OHA. The effect of 4OHA appeared to be dose dependent. Low doses (30 mg/kg and 50 mg/kg) induced significant changes in the estrogen and androgen responses, but the high dose (100 mg/kg) blocked all changes in sex steroids induced by Endo. 4OHA did not alter the Endo-induced changes in other steroids.     

Effect of some antiestrogens and aromatase inhibitors on androgen induced sexual behavior in castrated male rats

The effect of antiestrogens (MER-25, ICI-46474, and cis-clomiphene) and aromatase inhibitors (5-α-androstanedione, metopirone, and aminoglutethimide) on androgen induced copulatory behavior was tested in sexually inexperienced castrated male tats. Daily injections of 1 mg testosterone (T) for 21 days induced sexual activity in most subjects (61% mounting). Daily pretreatment with MER-25 or cis-clomiphene at three dose levels did not block the behavioral response to T. ICI-46474 at the high dose level (1 mg/kg) elicited a significant depressory effect on the sexual behavior of the T treated castrated rats. A single injection of 6 mg testosterone propionate (TP) induced mounting behavior in 56% of the tested rats within 120 hr. Treatment with metopirone or 5 α-androstanedione (injections every 12 hr for 96 hr) did not inhibit the response to TP. By contrast, aminoglutethimide (5 or 15 mg every 12 hr for 96 hr) abolished the behavioral response to androgen.     

Systematic studies invalidate the neonatally androgenized rat as a model for polycystic ovary disease

As an adult, the neonatally androgenized (AZ) rat is anovulatory and exhibits follicular cysts. Thus, the AZ rat has been used as a model for polycystic ovary disease (PCO). However, its correlation with the human disease is not clear; so we have studied the AZ rat to determine its suitability as a PCO model. In Experiment I, reproductive hormones were measured at specific intervals between postnatal Days 15 and 90 in saline-treated and AZ rats. In Experiment II, AZ rats were treated with exogenous follicle-stimulating hormone (FSH) or subjected to unilateral ovariectomy (ULO) as analogies to therapies that have been used to treat human PCO. The results demonstrate that the luteinizing hormone (LH), FSH, testosterone (T), and estradiol (E2) concentrations of the AZ rat were not different from control values. Additionally, FSH therapy did not increase the E2 concentrations or the ovarian weight of the AZ rat. Furthermore, control and AZ rats exhibited similar post-ULO rises in FSH, but compensatory ovarian hypertrophy was not evident in the AZ rat. We conclude that 1) the hormonal and morphological patterns observed in the AZ rat do not correlate with those of PCO and 2) the androgenized rat does not provide an adequate model to study PCO.     

Development of the vaginal epithelium showing estrogen-independent proliferation and cornification in neonatally androgenized mice.

Female mice of the C57 Black/Tw strain given 5 daily injections with 100 microng testosterone (T) or 5 alpha-dihydrotestosterone (DHT) from the day of birth showed estrogen-independent persistent proliferation and cornification of the vaginal epithelium in adulthood. The vaginal epithelium of the mice was essentially similar to that of the controls in histological structure during or shortly after neonatal injections of the androgens. In T- and DHT-mice aged over 20 days, however, a marked proliferation with or without superficial cornification took place in the epithelium lining the proximal and middle parts of the vagina (Müllerian vagina), while neither proliferation nor cornification occurred in the epithelium of the distal vagina (urogenital sinus vagina). On the second day of postnatal life in mice given a single injection with T on the day of birth, the mitotic activity in the epithelium of the middle vagina was heightened, but it dropped to the control level on the third day and remained low until 20 days. By contrast, the mitotic rates in the epithelium of the rest of the vagina in T-mice and of all parts of the vagina in DHT-mice were approximately the same as in the controls until 20 or 30 days. The mitotic rates in the epithelium of the Müllerian vagina were markedly elevated in T-mice at 20 days of age and DHT-mice at 30 days, and thereafter remained almost unchanged until 60 days of age. These results were different from the findings in mice given neonatal injections with the dose of estradiol-17 beta (E) capable of estrogen-independent vaginal cornification (Iguchi et al., 1976). The present finding seem to indicate that the mechanism involved in the induction of estrogen-independent vaginal changes by neonatal administration of androgen (T, DHT) is different from that following neonatal treatment with estrogen (E), although androgen and estrogen act directly on the vaginal epithelium of neonates.     

Alterations in the onset of ovulatory failure and gonadotropin secretion following steroid administration to lightly androgenized female rats

The present studies were designed to characterize the gonadotropin response to exogenous steroids in neonatally androgenized female rats in various states of reproductive decline. Female rats were androgenized by the administration of a single injection of testosterone propionate (TP) (10 or 100 micrograms) at 5 days of age. Control rats received sesame oil. Treatment with 100 micrograms TP resulted in persistent vaginal estrus (PVE) from the onset of vaginal introitus. Treatment with 10 micrograms TP resulted in a period of regular estrous cyclicity followed by PVE. In the first experiment, all animals were ovariectomized between the ages of 60-85 days and the gonadotropin response to exogenously administered estradiol benzoate (EB) (10 micrograms/100 g BW) and progesterone (P) (2 mg/animal) was determined. When testing began 3 days following ovariectomy, control females exhibited significant (P less than 0.01) afternoon elevations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) following EB, which were further amplified following P. When ovariectomy occurred prior to the onset of PVE (PRE PVE), lightly androgenized females (10 micrograms TP) showed no significant afternoon gonadotropin increase following EB. Following P, phasic LH secretion was present but significantly (P less than 0.01) decreased in amplitude and delayed in onset versus that of control females. When ovariectomy occurred 3 to 4 wk following the onset of PVE, lightly androgenized females (PVE group) as well as fully androgenized females (FAS) (100 micrograms TP) showed no gonadotropin response to steroid priming.(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of testosterone administration on plasma prolactin levels in the neonatally androgenized (NA) female rat

Neonatally androgenized (NA) female rats were ovariectomized (OVX) as adults and given 1 mg of testosterone propionate/day for 7 days and the plasma prolactin (PRL) pattern compared with NA intact animals and normal OVX animals given estrogen or TP. NA intact animals had elevated basal (morning values) and an attenuated afternoon surge when compared to normal estrogen-treated animals. Testosterone administration to normal animals induced an afternoon surge similar to that of normal estrogen-treated animals but the magnitude of the surge was less. Testosterone given to NA-OVX animals had little effect on either morning or afternoon PRL levels. The results suggest that in the NA rat the brain region involved in the conversion of testosterone to estrogen may be altered by neonatal androgen exposure.