Relationship of polycystic ovary induction to prolactin secretion: prevention of cyst formation by bromocriptine in the rat.

PRL levels were measured over 30 days of cyst induction in the rat. Polycystic ovaries (PCO) were induced by dietary incorporation of thiouracil (Thio) for 30 days and injection of 10 IU hCG sc for the last 20 days of the experimental period. Animals were killed at specific intervals 24 hours after the last injection. Ovaries and thyroids were removed and weighed. Sera were analyzed for PRL by RIA. PRL levels increased in animals receiving Thio plus hCG by day 30 compared to animals receiving Thio alone. The increase in PRL in the Thio, hCG-stimulated group coincides with formation of follicular cysts. Administration of bromocriptine (1 mg/day) concurrent with hCG during the last 20 days of Thio-feeding significantly suppressed ovarian weight gain and PCO formation. Serum PRL levels in bromocriptine-treated rats were significantly reduced compared to the PCO group yet were also significantly greater than all control groups at day 30. These findings suggest that PRL is important to the etiology of ovarian cysts in the rat.