Secretion of Prostaglandin F2α in Cycling and Pregnant Ewes1

Abstract

Indwelling cannulas were placed into a branch of the uterine vein and into the utero-ovarian vein of 10 nonpregnant ewes and into the utero-ovarian vein only of eight pregnant ewes. Blood samples were collected into chilled, heparinized tubes at 3-hr intervals from days 11 to 14 (three pregnant and five cycling ewes) or from days 14 to 17 (five pregnant and five cycling ewes) after estrus. Levels of prostaglandin (PG) F₂α were determined by radioimmunoassay. No significant difference was noted in mean levels of PGF₂α in the utero-ovarian vein between cycling (9.1 ± .6 ng/ml, n=458) and pregnant (8.1 ± .1 ng/ml, n=386) ewes. However, there was more variation (P<.01) in levels of PGF₂α in cycling ewes than in pregnant ewes. This was reflected by a greater number (P<.01) of peaks (any value greater than two standard deviations above the daily mean) of PGF₂α in cycling ewes than in pregnant ewes (32 vs 12). There was no significant difference in magnitude of peaks between cycling (41.3 ± 5.1 ng/ml) and pregnant (25.3 ± 7.4 ng/ml) ewes. It is suggested that decreased numbers of peaks of PGF₂α may be involved in the mechanism responsible for luteal maintenance in pregnant ewes. Copyright © 1976. American Society of Animal Science . Copyright 1976 by American Society of Animal Science.