Gonadotrophin Content of Pituitaries of Rats in Constant Estrus Induced by Continuous Illumination

Abstract

LH (luteinizing hormone) and total gonadotrophin of the anterior pituitaries of cycling rats under normal lighting and rats in constant vaginal estrus (CVE) induced by continuous illumination were compared. The ovarian ascorbic acid depletion method and the uterine weight increase in immature mice were employed for LH and total gonadotrophin assays, respectively. Most of the rats placed in constant light developed continuous vaginal cornification within 30 days. There was an increase in pituitary weight and the ovaries were smaller than those of the controls. The pituitary LH content and concentration were markedly decreased in rats in CVE after 50 and 100 days of illumination. Administration of progesterone, SC-13664 (an antiestrogenic compound), or clomiphene or oophorectomy caused an increase in LH. The pituitary total gonadotrophin of rats in CVE was similar to that of normal rats and increased under treatment with SC-13664 or clomiphene and after oophorectomy. Progesterone caused no change.