Pituitary regulation of serum calcium levels in the killifish, Fundulus heteroclitus L

Abstract

Hypophysectomy produced hypocalcemia in male killifish, Fundulus heteroclitus, adapted to calcium-deficient sea water. Such changes in serum calcium levels were corrected by intraperitoneal injections of a homogenate of whole pituitary glands or by transplantation of the gland to the musculature of the caudal peduncle. Injections of homogenates of the anterior or posterior parts of the pituitary gland were also effective while the homogenate of the middle part of the gland produced a smaller change. Injections with prolactin at the doses of 5, 2.5, and 0.5 μg per gram body weight per injection significantly increased the serum calcium levels of the hypocalcemic hypophysectomized fish. Cortisol (2.5 μg per gram body weight per injection) and ACTH (0.05 IU per gram body weight) were also hypercalcemic, but lower doses of ACTH (0.02 and 0.005 IU per gram body weight) and two doses of MSH (2.5 and 5 μg per gram body weight) were without effect. It is suggested that either ACTH, prolactin or both may have hypercalcemic effects on fish in calcium-deficient environments.