Plasma and pituitary hormone changes and follicular development after unilateral ovariectomy in cyclic rats

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Abstract
After unilateral ovariectomy of 4 day cyclic rats, plasma FSH increased over control values for 6-12 h after the surgery regardless of whether unilateral ovariectomy was performed before or after 0800 h on the day of diestrus, after which time compensatory ovulation did not occur at the next estrus. Pituitary content of FSH also increased from 6 h after unilateral ovariectomy. In contrast, plasma and pituitary levels of LH [lutropin] and prolactin were generally within the range of values of sham-operated rats. Treatment with pentobarbitone between 1300 and 1400 h on the day of proestrus in rats unilaterally ovariectomized after 0800 h on diestrus delayed the next spontaneous ovulation by 1 day and was accompanied by a rise in plasma FSH concentrations for 24 h and a doubling in the number of ovulations from the remaining ovary. Follicle counts showed an increase in large healthy follicles (.gtoreq. 501 .mu.m diameter) and a decrease in atretic follicles in pentobarbitone-treated rats. The FSH rise induces compensatory follicular development and decreases follicular atresia when there is sufficient time for follicles to develop before the LH surge.