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)

Mechanism of reproductive deficiency in spontaneously hypertensive rats.

Spontaneously hypertensive rats (SHR) show multiple endocrine disorders. In the present work, specific reproductive modifications were analysed using normotensive Wistar-Kyoto rats (WKY) as controls. SHR showed delayed vaginal opening and first estrus presentation, regular vaginal cycles and released a normal number of ova each cycle. When compared with controls, SHR showed a decrease in the percentage of successful pregnancies (69% vs. 86% in WKY) and in the litter size (7.83 +/- 0.5 vs. 10.41 +/- 0.5). In SHR, progesterone plasma levels were significantly increased during the days 1-14 of pregnancy, and on the 5th day of pregnancy the plasma concentrations of LH but not of FSH were enhanced. Mortality during the first month of life was higher in SH (50%) than in control (24%) strain. When the SH females were mated with Wistar or WKY males, the percentage of pregnancies rose up to 95%. On the contrary, Wistar or WKY females mated with SH males showed a decrease in the percentage of pregnancies (62.5% and 50%, respectively). Besides, the litter sizes were significantly reduced in Wistar females mated with SH males. Newborn SH suckled immediately after birth from a WKY mother showed a significant reduction in the mortality during the first month of life (8% vs. 50%). In conclusion, our results suggest that changes in fertilization and/or implantation processes of SH rats were responsible for the reduced pregnancy rate, whereas the increased neonatal mortality could be due to lactation activity of SH mothers.

Normoprolactinaemia in spontaneously hypertensive rats: absence of a close relationship between plasma concentrations of prolactin and systolic blood pressure.

Prolactin has been involved in different types of hypertension both in man and in rats. In an attempt to substantiate this hypothesis, we have analysed the correlation between plasma concentrations of prolactin and systolic blood pressure (SBP) in female and male rats from spontaneously hypertensive (SH) and normotensive Wistar-Kyoto strains (30, 60 and 90 days old), as well as in adult female Wistar rats rendered hyperprolactinaemic by the administration of 100 micrograms testosterone propionate on day 1 of life, or adult males with low plasma concentrations of prolactin after administration of bromocriptine (4 mg/kg per day) over 15 days. Our results indicate a lack of correlation between plasma concentrations of prolactin and SBP since plasma concentrations of prolactin were normal in male and female SH rats and hyper- and hypoprolactinaemia did not affect SBP. In spite of these normal plasma concentrations of prolactin, SH rats showed subtle changes in the secretion of this hormone in vitro and in vivo in response to exogenous serotonin administration and to immobilization.

[Body development and puberty in spontaneously hypertensive rats]. / Desarrollo corporal y pubertad en ratas espontáneamente hipertensas.

The body growth and the onset of puberty in spontaneously hypertensive rats (SHR) and in normotensive controls (WKY) have been studied. In female rats the onset of puberty was determined by both the age and the body weight at which the vaginal opening and first estrus appeared, as well as the ability of estradiol and progesterone to induce pituitary LH release. For this purpose females were injected with estradiol benzoate (0.1 mg/kg) and progesterone (1 mg/rat). Control animals received only oil vehicle. In male rats, puberty was assessed by studying the age and body weight at the time of balano-preputial separation. In another experiment, SH and WKY rats were decapitated on day 30 to determine FSH, LH, PRL, GH and testosterone plasma levels in males and FSH and LH in females. The results obtained show: a) A greater body weight, at all the ages studied (every 4 days between days 28 and 92) in SHR animals. b) A delay in vaginal opening and first estrus presentation in SHR females. c) Absence of spontaneous LH peaks in WKY females. d) Advancement in balano-preputial separation in SHR males and e) Higher plasma FSH levels in SHR males than in WKY males, without differences in other hormones.