The effects of hypophysectomy and replacement therapy with prolactin,cortisone, or their combination on the blood of the black bullhead Ictalurus melas

Experiments are done on intact and hypophysectimized Ictalurus melas maintained in approximately isotonic saline. Serum Na⁺ decreases after hypophysectomy but serum Cl^? is not affected. Prolactin increases both serum Na⁺ and Cl^? in intact fish, but only Na⁺ increases in hypophysectomized recipients. Cortisone decreases serum Na⁺ in hypophysectomized fish but increases serum Cl^?. When prolactin and cortisone are administered together, the Na⁺-increasing effect of prolactin is dominant, while the Cl^?-increasing effect of cortisone is greatly enhanced. It is concluded that the two ions are regulated separately and that both hormones are necessary to maintain normal levels in hypophysectomized recipients. Serum Ca²⁺ is higher in adult females than in males and low in juveniles, irrespective of treatment. Serum inorganic P is lower in juveniles than in adults and is unaffected by hypophysectomy. Serum organic P increases in hypophysectomized fish receiving cortisone, perhaps in correlation with the increase in serum proteins. Saline injections are hyperglycemic in intact fish but prolactin injections are hypoglycemic, as is hypophysectomy. Serum cholesterol tends to increase after hypophysectomy and injections of prolactin and/or cortisone result in a significant decrease. No sexual differences in serum proteins are detected in adult, postspawning fish and hypophysectomy has no effect in September, but low levels characterize winter fish at low temperature. Cortisone increases serum proteins in hypophysectomized fish in winter, but otherwise no hormonal effects are observed. Prolactin significantly lowers the pH of the blood, alone or in combination with cortisone.