The Temporal Pattern of LH, FSH, and Ovulatory Responsiveness To Luteinizing Hormone Releasing Hormone in the Cyclic Hamster

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Abstract
LH [luteinizing hormone] and FSH [follicle stimulating hormone] were measured by radioimmunoassays in hamsters injected s.c. with LHRH [LH-releasing hormone] on each day of the estrous cycle. The ovulatory dose of LHRH required to reverse the phenobarbital-block in proestrous (day 4) hamsters was 100 ng as a single injection or 50 ng as 2 injections 2 h apart while a 10-fold greater dose was required in day 3 animals. Hamsters injected on day 1 or 2 could not be induced to ovulate with up to a total of 4 .mu.g LHRH. LHRH generally resulted in significant increases in LH and FSH on all days of the cycle including larger pre- to posttreatment rises on days 2 and 3 than on day 1 and, with smaller LHRH doses, potentiation of LH and FSH release on days 3 and 4.