SIMULTANEOUS INFUSION OF PROSTAGLANDIN E2 ANTAGONIZES THE LUTEOLYTIC ACTION OF PROSTAGLANDIN F2α IN VIVO

Abstract

SUMMARY: Corpora lutea of ewes bearing ovarian autotransplants were infused for 4 h with prostaglandin F_2α (PGF_2α) (10 μg/h), PGF_2α + PGE₂ (10 μg/h of each), PGE₂ (10 μg/h) or saline on day 10 of the cycle. Ovarian venous blood obtained before, during, and up to 12 h after the infusion period, was assayed for progesterone. Prostaglandin F_2α produced an immediate, rapid and sustained decline in progesterone secretion, but infusion of PGE₂ together with PGF_2α prevented the decline until after the infusion. Progesterone secretion was unaffected by infusion of PGE₂ alone. Oestrous behaviour was observed in four out of seven animals infused with PGF_2α but in only one out of six infused with PGF_2α + PGE₂. None of the animals infused with PGE₂ alone or saline only came into heat.