A histochemical study of the respiratory system in rabbit ovarian follicles during ovulation

: Histochemical studies on the activities of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), succinate dehydrogenase (SDH) and cytochrome oxidase (CY-O) in rabbit ovarian follicles at various times after the administration of hCG were performed to investigate the relationship between the activities of steroid biosynthesis and the respiratory system. The activities of 3 beta-HSD and SDH were studied by using the tetrazolium salt and CY-O activities by the method of Seligman with prefixation. On the granulosa cell layer prior to the administration of hCG, no activities of 3 beta-HSD and CY-O were detectable, while slight activities of SDH were observed. These three enzymes showed intense activities on the granulosa cell layer 3 hours after the administration of hCG, which were maintained till the time of ovulation. The results indicated that increased activities of steroid biosynthesis in the granulosa cell layer after LH-surge were accompanied by the accelerated TCA cycle and respiratory chain. Energy from accelerated glycolysis may be utilized for steroid biosynthesis in preovulatory granulosa cells. Increased O2 consumption due to accelerated aerobic glycolysis is in accordance with hyperactivity of perifollicular capillaries, which finally leads to rapid follicular expansion and ovulation.