INDUCTION BY ESTRADIOL-17-BETA OF POLYCYSTIC OVARIES IN THE GUINEA-PIG

In the present study we wished to develop a model for polycystic ovari an syndrome (PCOS) using the guinea pig, because this animal's cycle, compared to other rodent models, more closely emulates that of humans. Four silastic capsules, either empty or containing cholesterol or est radiol-l7beta, were placed subcutaneously for 48 h on Day 10 or 12 of the cycle. Vaginal smears were taken daily. Cardiac blood was drawn at various intervals. At necropsy, trunk blood was collected and ovaries were excised and analyzed histologically. Cycle length was extended o ver that in controls in animals treated with estradiol-17beta (E2) on Day 12 of the cycle. Treatment with E2 resulted in an increase in seru m estrogen 2 h after capsule insertion. No changes were evident in pro gesterone or androstenedione concentrations with treatment. Animals tr eated with E2 and killed late (54 days after capsule removal) showed c ysts grossly (group A), while occult cysts were present in E2-treated animals killed early (17 days; group B); no cysts were observed in con trol groups. Ovarian weight and size were increased in group A over co ntrols. There was an increase in the fraction of atretic:total follicl es < 500 mm in size in group A compared to group B as well as compared to controls. Since these results are similar to those seen in human P COS, we conclude that the guinea pig may serve as an exceptional and u nique model for the study of PCOS and may be applicable to humans.