Ovarian hyperstimulation in rats.
Induction of a mild hyperstimulation syndrome in the female rat, and the possible effect of the induction on prolactin, were studied using light and electron microscopy as well as radioimmunoassay. Five days of human menopausal gonadotropin (HMG) treatment were followed by human chorionic gonadotropin (HCG) administration. Ovarian hyperstimulation was observed in all treated rats, as attested to by the weight increase and by histological studies. Ovaries were enlarged 3-4 times as compared with controls, and consisted mostly of corpora lutea follicular cysts and hemorrhagic cysts. Other visceral organs remained unaffected, except for slight edematous changes observed in the lungs of the treated rats. Electron microscopic examination of the hypophysis of the treated group tends to indicate increased synthesis and secretory activity of the prolactin cells. However, serum prolactin levels of treated and non-treated groups were not different. Augmented doses of the gonadotropins did not change the findings, and only mild grade 2 ovarian hyperstimulation, according to Schenker and Weinstein (1978), could be produced in the mature rat. Thus, the rat experimental model does not seem to be comparable with the situation in the human, and cannot be used to study the pathogenesis of the disorder in the human.