Inhibition of implantation by the administration of anti-LHRH immunogamma globulin in rats

Antibody against synthetic LHRH was generated in ewes by repeated intradermal injection with Glu(I)-LHRH coupled with human serum albumin and then separated anti-LHRH gamma globulin (A-LHRHγG) by ammonium sulphate precipitation technique. Daily injection of A-LHRHγG from day 1 through day 7 (1ml,iv), caused delayed implantation for 7-8 days and only 2 in 5 rats could maintain normal pregnancy course until term. Control rats in which normal sheep gamma globulin (NSG) was injected under the same protocol, could undergo normal fetal development. Daily injection of A-LHRHγG from day 3 through day 5 delayed the nidation process for 4-6 days. Plasma estrogen in the A-LHRHγG treated rats was maintained at low levels, and raised significantly on day 4 and 5 in NSG treated control rats. A single injection of 1 ml of A-LHRHγG on day 4 inhibited implantation on day 8, but injection on day 3 or 5 did not. Delayed implantation by A-LHRHγG injected on day 4 was overcome by concomitant administration of 2 subcutaneous injections of Iug of synthetic LHRH, or single subcutaneous injection of Iug of E₂. The results indicate that the hypothalamic LHRH is essential on day 4 of pregnancy for timely implantation of fertilized ova, presumably by maintaining LH and consequently estrogen secretion from ovaries.