Effects of hypophysectomy, pituitary gland homogenates and transplants, and prolactin on photoreceptor destruction.

Prepubertal removal of the pituitary gland, which in young animals influences sexual maturation, reduces significantly the amount of retinal photoreceptor destruction when the rats are exposed to continuous illumination in adulthood. When crude pituitary gland homogenate is administered to adult rats hypophysectomized prior to puberty, photoreceptor destruction is more severe. Transplantation of whole pituitary glands to the kidney capsule of hypophysectomized rats also reduces the effect of pituitary gland removal and results in more extensive damage to receptor cells than found in hypophysectomized, adult animals. Hypophysectomized rats treated with prolactin had more severe retinal damage than untreated, hypophysectomized rats. The injection of pregnant mare serum and human chorionic gonadotropic hormones into hypophysectomized rats was not effective in reversing the protection afforded by hypophysectomy. Results of these studies indicate the hormones of the pituitary gland have a regulatory influence on the severity of light-induced, retinal photoreceptor damage in the rat.