Induction of polycystic ovarian disease in rats by continuous light. I. The reproductive cycle, organ weights, and histology of the ovaries

Changes in the estrous cycle, organ weights, and histology of the ovaries were investigated in a group of adult albino rats exposed to constant light. By the end of 6 weeks of constant light exposure, 56 of 60 rats (93.3 per cent) showed persistent vaginal estrus—as defined by the presence of at least 10 consecutive days of vaginal cornification. Although there was a progressive atrophy (decrease in weight) of the ovaries, the adrenals were initially hypertrophied (increase in weight), but they eventually became atrophied as the duration of constant light was advanced. The most consistent finding of the polycystic ovaries in the constant-light-treated rats was the presence of markedly distended and cystic tertiary follicles. On changing the light schedule from constant light to light-dark, not only the estrous cycles reappeared, but also the ovaries became normal in gross as well as microscopic appearance. On the basis of the present study and other studies, it is concluded that polycystic ovaries due to constant light exposure in rats represent a progressive multiglandular endocrinopathy.