Effect of estrogen on postovulatory LH surge in baboons.

In normally cycling female baboons, an LH surge appeared prior to ovulation, in addition, another LH surge (postovulatory LH surge) was observed within two days after ovulation. An attempt was then made to determine the effect of postovulatory LH on the luteinization of corpus luteum in baboons. Injections of 300 micrograms estradiol benzoate were given at 09.00 and 16.00 hr daily for 5 days following ovulation; the plasma level of LH was increased, but plasma progestin was suppressed. These results infer that the injected estrogen (estradiol benzoate) may inhibit the luteotrophic effect of postovulatory LH on the corpus luteum, therefore, plasma progestin remains lower even though postovulatory LH is elevated.