Temporal Aspects of the Regulation of Corpus Luteum Function by Luteinizing Hormone, Prolactin and Placental Luteotrophin During the First Half of Pregnancy in the Rat12

Abstract

Intact rats were injected once, subcutaneously, with either 1.0 mg of ergocornine, free base (ECO), to prevent prolactin release, or an equine antiserum to bovine LH (LH-AS), to neutralize endogenous LH, on one of the days between days 6 and 12 of pregnancy. ECO treatment was uniformly abortifacient on day 6, only slightly less so on day 7, and was ineffective at 0400 hr or later on day 8. LH-AS treatment on day 6 or 7 induced abortion in very few rats; at 0400 hr on day 8, it induced abortion in 92%, and at 1200 or 1600 hr on day 8 or at 1200 hr on day 10, in 100% of the rats; when given on day 12, it was again ineffective. ECO did not depress serum LH or FSH levels, but abolished the nocturnal surge of prolactin; ECOinduced abortions could be prevented by treatment with prolactin but not with LH. Absorption of the LH-AS with LH, but not with either FSH or bovine serum abolished its abortifacient effect. A severe fall in the serum progesterone level occurred within 12 to 48 hr after treatment with either...