Long-term chronic stress exposure induces PCO phenotype in rat

Thus far the effects of chronic stress on the ovary were studied for shorter durations. However, responses of the ovary may vary with durations of exposure to stress. Hence, we investigated the responses of the ovary following exposure to different durations of chronic stress. Exposure of rats to restraint (1 h) and after a gap of 4 h to forced swimming (15 min) daily for 4 or 8 weeks resulted in significant decreases in the activities of the ovarian antioxidant enzymes, 3β-hydroxysteroid dehydrogenase and percentage of healthy granulosa cells with concomitant increases in the number of atretic follicles, the percentage of apoptotic granulosa cells and ovarian malondialdehyde concentration. However, the response of the ovary to similar stress regime for 12 weeks was paradoxical as there were increases in the activities of ovarian antioxidant enzymes and 3β-hydroxysteroid dehydrogenase, the number of healthy antral follicles, and decreases in ovarian malondialdehyde concentration and percentage of apoptotic granulosa cells. These changes were accompanied by hyperglycaemia and an increase in the serum levels of insulin, testosterone and oestradiol. In addition the cystic follicles were found in the ovaries of these rats. However, the number of oestrous cycles and active corpora lutea showed significant decrease in all the durations of stress exposure. The results demonstrate a differential response of ovary to short- and long-term exposure to chronic stress.