Delayed Implantation Caused by Administration of Sheep Immunogamma Globulin against LHRH in the Rat 1

Summary

The effect of the administration of sheep anti-LHRH gamma globulin (anti-LHRH-G) on implantation of fertilized ova was investigated in rats. Daily injections of 1 ml of anti-LHRH-G from Days 1 through 7 of pregnancy uniformly inhibited implantation of fertilized ova on Day 8, but viable sites, though considerably smaller in size than in control rats, became distinguishable on Day 14 in most rats. In some of these rats resorption of fetuses occurred, and others delivered pups 7-8 days after term. When the rats were given anti-LHRH-G from Days 3 through 5, the implantation was delayed by 5 days, but the gestation was not terminated. A single injection of 1 ml of anti-LHRH-G on Day 4 inhibited implantation on Day 8, but injection on Day 3 or 5 did not. The delayed implantation by anti-LHRH-G injected on Day 4 was nullified by concomitant administration of 2 sc injections of 1 μg of LHRH, or a single dose of 1 μg of estradiol. The data indicate that the hypothalamic LHRH is essential on Day 4 of pregnancy for timely implantation of fertilized ova, probably by maintaining LH and, consequently, estrogen secretion.