Effect of ACTH and Vasopressin on Serum Calcium and Citrate Levels in the Rabbit

Porcine ACTH (200 U/mg) lowers serum calcium levels and raises serum citrate levels significantly in the fasting rabbit within 2 hr after intramuscular injection of 16 μg/kg of the material. A polypeptide comprising the N-terminal 24 amino acid residue of beta-corticotropin also has this property. Synthetic lysine vasopressin (270 U/mg) lowers serum calcium levels to a lesser extent but causes a depression of citrate levels. Crude acid extracts of the porcine posterior pituitary gland with vasopressin activity elevate citrate levels. Further, they depress calcium levels to a greater extent than synthetic lysine vasopressin. Fractionation of this material, first on the DEAE-cellulose column and then on the carboxy methyl cellulose column, yielded a fraction with 131 U/mg of vasopressin activity, which elevated citrate levels and depressed calcium levels in the rabbit. This material was not homogeneous as determined by acrylamide gel electrophoresis. (Endocrinology 77: 108, 1965)