Oestradiol-17 , progesterone, FSH and LH in prepubertal calves induced to superovulate

Abstract

Fluorogestone acetate (vaginal sponge for 4 days) and PMSG [pregnant mare''s serum gonadotropin] (i.m. injection at the time of sponge insertion) treatment was administered to seven 3-mo. old calves to induce superovulation. Samples of peripheral plasma were taken every 4 h during treatment (4 days) and then every 2 h for 7 days. FSH [follicle stimulating hormone], LH [luteinizing hormone], estradiol and progesterone were measured by radioimmunoassays. In all calves estradiol concentrations increased 24 h after PMSG injection, and reached the highest levels (41-502 pg/ml) during the preovulatory surge of both gonadotropins. The surge of LH and FSH occurred from 12-22 h after cessation of treatment. The maximum levels of LH and FSH were 11-72 ng/ml and 23-40 ng/ml, respectively, and occurred within 4 h of each other. Between 40-68 h after the LH peak the concentrations of progesterone began to increase from basal values, reaching 24.0-101.7 ng/ml when the animals were killed. A quantitative relationship was found between plasma estradiol concentration and the numbers of ovulating follicles. Progesterone levels seemed to be related to the numbers of corpora lutea and to the numbers of unovulated follicles. Gonadotropin output was not quantitatively related to ovarian activity or steroid secretion.