title: Platelet-activating factor alters the dynamics of prostaglandin and protein synthesis by endometrial explants from pregnant and cyclic cows at day 17 following estrus.
abstract: Factors produced by bovine conceptuses alter prostaglandin (PG) and protein secretion by endometrial explants from cyclic cows and induce an intracellular inhibitor of PG synthesis. Endometrial explants from cyclic (n = 4) and pregnant (n = 3) cows at Day 17 following estrus were incubated for 24 h with 0, 0.1, 0.5, 1 and 5 microg platelet-activating factor (PAF)/ml. Cotyledonary microsomes from parturient cows were utilized to determine levels of an intracellular/cytosolic inhibitor of PG synthesis. Endometrial explants from additional cyclic cows (n = 4) were incubated for 24 h with 0 or 5 microg PAF/ml with and without 50 microCi [(3)H]leucine. Endometrial explants (cyclic cows, n = 3) were also incubated for 12 h with each of the following treatments: 1) Control; 2) PAF (1 microg/ml); 3) lyso-PAF (2 to 10 microg/ml); 4) PAF-receptor antagonist (2 to 10 microg/ml); 5) PAF (1 microg/ml) + antagonist (2 to 10 microg/ml); 6) bovine conceptus secretory proteins (bCSP; 25 microg/ml); and 7) bCSP (25 microg/ml) + antagonist (5 microg/ml). Platelet-activating factor had distinct negative and positive dose effects on PGF and PGE-2 secretion, respectively, by explants from cyclic cows, whereas PG secretion was not altered by PAF in the endometrium of pregnant cows. Platelet-activating factor did not alter the level of an intracellular inhibitor of prostaglandin synthesis, whereas, bCSP increased the level of this inhibitor. Platelet-activating factor decreased the incorporation of [(3)H]leucine into tissue and secreted proteins for explants from cyclic cows. Lyso-PAF did not alter endometrial prostaglandin secretion. The effects of PAF but not of bCSP were blocked by the PAF-receptor antagonist. Platelet-activating factor altered PG and protein secretion by the endometrium from cyclic cows, and it may be a potential regulatory factor during early pregnancy if secreted by the bovine conceptus.
authors.affiliation: Dairy Science Department, University of Florida, Gainesville, FL 32611-0701, USA.
authors.forename: T S
authors.initials: TS
authors.lastname: Gross
authors.forename: W W
authors.initials: WW
authors.lastname: Thatcher
authors.forename: C
authors.initials: C
authors.lastname: O'Neill
authors.forename: G
authors.initials: G
authors.lastname: Danet-Desnoyers