Evidence for prostaglandin involvement in early luteal regression of the superovulated nanny goat (Capra hircus).
Feral ♀ goats of various ages were treated with intravaginal progestogen sponges for 16 days to synchronize oestrus. On day 2 before sponge removal, the goats were given 1200 IU PMSG to induce superovulation; 6 of the goats were also injected every 12 h with flunixin meglumine, a PG synthetase inhibitor, from days 3 to 7 of the synchronized oestrous cycle. Jugular blood samples were collected from all ♀♀ into heparinised syringes at daily intervals over the 2 days before sponge removal, twice daily for the next 2 days, then at hourly intervals from 09.00 to 17.00 h for 2 days and then twice daily for a further 2 days, for measurement of the plasma concentrations of progesterone and the PGF metabolite 13,14-dihydro-15-keto-PGF (PGFM) by radioimmunoassay. Intermittent surges in plasma PGFM concentration were observed in hourly samples collected from all 4 untreated ♀♀ but in only 2 of the 6 inhibitor-treated ♀♀ (P<0.05), and the peak plasma PGFM concentration was reduced in these 2 inhibitor-treated goats compared with the control goats. The corpora lutea of the inhibitor-treated ♀♀ appeared to be functional, as indicated by the plasma progesterone profile and endoscopic examination of the corpora lutea. In the control ♀♀, however, there was evidence of premature regression of corpora lutea. These results suggest that the premature release of PGF2α may be the cause of premature regression of corpora lutea in ♀ goats induced to superovulate.