Intrauterine Infusion of High Doses of Pig Trophoblast Interferons Has No Antiluteolytic Effect in Cyclic Gilts(1)
In most mammals, establishment of pregnancy requires the continuation of progesterone production by the corpus luteum (CL) beyond the luteal phase of the estrous cycle. In ungulates, this phenomenon relies on a signal delivered by the trophoblast of the periimplantatory conceptus that blocks or attenuates the production of luteolysin prostaglandin F2„ (PGF2q) by the endometrium (see for recent reviews). buy levaquin online
In pigs, the initial antiluteolytic signal is delivered on Days 11-12 of pregnancy and is generally considered to be mediated by estrogens released by the conceptus. Indeed, estrogens are synthesized by the trophoblast during this period, and it has been shown that injection of a large amount of estrogens between Day 11 and Day 15 causes pseudopregnancy in cyclic females. More precisely, it has been shown that extended luteal maintenance required two periods of estrogen treatment: one on Day 11 and a second around Days 15-18, correlating well with the normal pattern of estrogen release by the pig conceptus during these periods [7, 8]. However, intrauterine infusion of estrogens at doses similar to those physiologically produced by conceptuses delays luteolysis for a few days only, suggesting that other factors might be involved. However, in other experiments, daily infusion of total conceptus secretory proteins did not prolong CL maintenance.
Tags: Interferons, Intrauterine Infusion, Pig, Trophoblast