THE EFFECT OF PROSTAGLANDIN F2α ON PROGESTERONE, OESTRADIOL AND LUTEINIZING HORMONE SECRETION IN SHEEP WITH OVARIAN TRANSPLANTS

Abstract

SUMMARY: The luteolytic properties of prostaglandin F_2α (PGF_2α) were studied in experiments on sheep with ovarian autotransplants. PGF_2α was infused at the rate of 40, 10 and 2 μg/h for 4·0, 7·0 and 9·5–18·0 h respectively. At rates of 40 and 10 μg/h, progesterone secretion decreased to 50% of the control levels in 2·6 ± 1·4 h and fell to 8–30 μg/h within 36–52 h from the start of infusion. The onset of oestrus occurred 42–66 h after the infusions had started and a typical pre-ovulatory surge of luteinizing hormone (LH) was observed 52–66 h after infusing PGF_2α. On occasions, this surge was accompanied by a brief peak of oestradiol-17β secretion and shortly thereafter ovarian steroidogenesis decreased to very low levels. In four sheep infused at a rate of 2 μg/h, peripheral progesterone values decreased gradually and only one animal returned to oestrus. It would seem that 2 μg/h is close to the minimum intra-arterial dose to cause luteolysis in the sheep.