Lack of effects of indomethacin on estradiol feedback control of luteinizing hormone in ovariectomized ewes.
We tested the hypothesis that indomethacin, a potent inhibitor of prostaglandin synthesis, would modify estradiol's effects on tonic and surge concentrations of LH in chronically ovariectomized ewes during the anestrous season. Ewes (n = 21) were assigned randomly to one of four treatments: Vehicle+Blank (n = 5); Indomethacin+Blank (n = 6); Vehicle+Estradiol (n = 5); or Indomethacin+Estradiol (n = 5). On d=0 (hr = 0), ewes began to receive i.m. injections of either indomethacin (4 mg/kg body weight) or corn oil every 8 hr for 9 d. Blood samples were collected every 12 min for 6 hr beginning at -6 hr, +18 hr, and on day 8 (relative to initial injections of indomethacin or vehicle) to assess tonic patterns of secretion of LH. At +24 hr, ewes received blank- or estradiol-containing Silastic implants and were bled hourly for 48 hr. On day 9, ewes received 50 micrograms of GnRH i.v. and were bled hourly for 8 hr. Serum samples were assayed for LH. Indomethacin had no effect on the following parameters of LH secretion: 1) mean concentrations (ng/ml; 8.4 +/- .7 vs 8.9 +/- .8; P > .1), 2) pulse frequency/6 hr (4.5 +/- .4 vs 4.1 +/- .4; P > .1) or 3) pulse amplitude (ng/ml; 15.3 +/- 1.1 vs 14.9 +/- 1.2; P > 1). Estradiol elicited a surge of LH which began 18.9 +/- 1.7 hr after implant insertion, reached a mean peak concentration of 95.3 +/- 20.1 ng/ml, and did not differ with respect to indomethacin treatment (P > .1).(ABSTRACT TRUNCATED AT 250 WORDS)
Bettencourt
C M
CM
Animal Sciences Department, University of Missouri, Columbia 65211.
Moffatt
R J
RJ
Keisler
D H
DH
D000704:Analysis of Variance; D000780:Anestrus / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D004343:Drug Implants; D004347:Drug Interactions; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D005246:Feedback / Q000187:drug effects; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007213:Indomethacin / Q000008:administration & dosage / Q000494:pharmacology*; D007273:Injections, Intramuscular / Q000662:veterinary; D007986:Luteinizing Hormone / Q000097:blood*; D010052:Ovariectomy / Q000662:veterinary; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D011897:Random Allocation; D012756:Sheep / Q000378:metabolism*
D004343:Drug Implants; D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007986:Luteinizing Hormone; D007213:Indomethacin