The effects of unilateral ovariectomy on follicular maturation in the hamster.

In the hamster, the follicles that will ovulate at any one estrus can usually be distinguished by the third day of the estrous cycle. This has been shown by determining whether compensatory ovulation occurs after unilateral ovariectomy on the various days of the estrous cycle. The results indicate that unilateral ovariectomy on the first and second day of the cycle is followed by a doubling in the number of ova released from the remaining ovary. There is no compensatory increase in ovulation after unilateral ovariectomy on the third or fourth day. However, if pregnant mare serum or human chorionic gonadotropin is injected at the time of unilateral ovariectomy on the third day the ovulation rate is doubled in the remaining ovary. The altered responsiveness of the ovary in the latter half of the cycle is paralleled by accelerated growth of the largest follicles as the antra begin to expand. It is believed that a shift in the ratio of FSH and LH at midcycle accounts for the difference in results when unilate...