Corpus Luteum Function After Indomethacin Treatment During the Estrous Cycle and Following Hysterectomy in the Gilt

Abstract

Indomethacin (IND), a prostaglandin synthetase inhibitor, was used to determine the relationship between prostaglandin (PG) secretion and corpus luteum (CL) function during the luteal phase of the estrous cycle and after hysterectomy in the gilt. In Experiment 1, gilts that had displayed estrous cycles of 18 to 22 days (onset of estrus = Day 0) were randomly assigned to four treatments (n = 7/group): 1) ethanol vehicle (EtOH) daily from Day 10 through Day 17; 2) IND daily from Day 10 through Day 17;3) IND daily from Day 10 through Day 13 and EtOH daily from Day 14 through Day 17; and 4) EtOH daily from Day 10 through Day 13 and IND daily from Day 14 through Day 17. In Experiment 2, 15 gifts were hysterectomized on Days 6 to l0 of the estrous cycle and were randomly assigned to a control (n = 7) or IND-treated (n = 8) group. Treatment, daily for 4 days, began when all gilts had reached Day 18 or later. The daily dose of 10 mg IND/kg BW was calculated on the average body weight of each treatment group. In Experiment 1, ovarian morphology at necropsy on Day 25, serum progesterone and 13,14-dihydro-15-keto prostaglandin F_2α (PGFM) concentrations throughout the experimental period, and failure to display estrus by Day 25 suggest that IND treatment during the luteal phase of the estrous cycle prolonged CL maintenance in the pig. The progesterone and PGFM assays were validated in our laboratory. In experiment 2, CL morphology and serum progesterone and luteinizing hormone (LH) concentrations indicate that IND treatment failed to affect luteal function by a direct action on the luteal cell or by suppressing pituitary LH secretion.