Circulating Levels of Chorionic Gonadotropin and Progesterone in the Rhesus Monkey Treated with LH Antiserum during Early Gestation1

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Abstract
Antiserum to ovine luteinizing hormone was prepared in rabbits by the multiple intradermal technique. Ouchterlony double immunodiffusion tests and biological neutralization experiments in rats as well as in a cyclic rhesus monkey revealed that this LH antiserum (LH-A/S) contained specific antibodies for rhesus LH. No cross reactivity was observed with monkey chorionic gonadotropin (mCG). Similar observations were made in a modified radioimmunoassay, which produced parallel inhibition curves with a purified rhesus monkey LH reference preparation and a serum pool obtained from spayed monkeys. Three ml of this LH specific antiserum or normal rabbit serum (NRS) were administered i.m. twice daily to pregnant rhesus monkeys on Days 15-19 of gestation. Daily blood samples were drawn by femoral venipuncture and the sera assayed by RIA from mCG, progesterone and circulating levels of LH antibodies. All monkeys treated with LH-A/S, as well as NRS, maintained pregnancies as evidenced by normal circulating levels of mCG and pregnancy positive rectal palpation on Day 30 or 35 of gestation. Serum progesterone levels were not significantly different in these groups of animals. Circulating LH antibodies were present even after discontinuation of LH-A/S treatment. These observations suggest that LH is not a luteotropic hormone during the period following CL rescue and until Day 21 of gestation in the rhesus monkey. The normal levels of mCG and progesterone in LH-A/S treated animals strongly support the concept that mCG is the luteotropic principle during this portion of gestation in this species.