UNILATERAL OVARIECTOMY INCREASES LOSS OF PRIMORDIAL FOLLICLES AND IS ASSOCIATED WITH INCREASED METESTRUS CONCENTRATION OF FOLLICLE-STIMULATING-HORMONE IN OLD RATS

The primary objective of these studies was to determine whether unilateral ovariectomy (ULO) would affect rate of loss of primordial follicles. In experiment 1, retired breeder rats, unilaterally ovariectomized and maintained on the experiment for 90 days after surgery, had fewer (p < 0.01 ) primordial follicles per ovary than sham-operated controls of the same age. The purpose of experiment 2 was to determine whether time after ULO or age of rats was the critical factor necessary for increased loss of primordial follicles found after ULO in experiment 1. It was found that age was more important than time: when ULO was performed at 30 days of age, the number of primordial follicles did not decrease in ULO rats compared to controls (p > 0.05) before 250 days of age. Concentrations of FSH during metestrus were not greater (p > 0.05) in ULO rats than in controls until rats were 250 days old. There were also fewer (p < 0.05) growing follicles per ovary in ULO than in sham-operated rats at 250 days of age. It is concluded that ULO can increase the loss of primordial follicles, but only in old rats (greater-than-or-equal-to 250 days of age).