Patterns of Luteinizing Hormone in Serum Following Administration of Stalk-Median Eminence Extracts to Rhesus Monkeys1

Concentrations of luteinizing hormone (LH) were determined in serum samples collected from the femoral vein of rhesus monkeys at 5-15-min-intervals following administration of ovine stalk-median eminence extract (SMEE). Following iv injections of .02-.32 eq SMEE, a dose-related response was observed in serum LH. A marked increase in LH of 3-50 × baseline occurred within 5 min of SMEE injection. This rise in serum LH returned to baseline within 60-90 min. Chronic iv infusion of SMEE for 5-6.5 hr elicited an immediate rise in serum LH and a plateau which lasted until the infusion ceased. The increased concentrations of serum LH prompted by equivalent dosages of SMEE given at Days 5-7, 9-13, or 19-23 of the menstrual cycle or following injection of 0.5 mg of progesterone sc on days 6-12 were comparable. Antiestrogen, U-11, 100A injected sc at 0.5 mg daily on days 7-12, significantly reduced the LH released by SMEE injections. The decreased response to SMEE stimulus following antiestrogen, but not progesterone injections, suggest these compounds influence LH release via different mechanisms. In control, progesterone- and antiestro-gen-treated monkeys the iv injection of SMEE did not induce ovulation, whereas two of three “progesterone-blocked” females did ovulate following a 5-6.5 hr chronic infusion indicating the duration of LH elevation was critical.