Effect of vasopressin structural modifications on rat renal excretion of Na, K, and water

¹ Laboratorío de Fisiología, Escuela de Medicina, Universidad Católica de Chile, Santiago, Chile

Lys8-vasopressin was incubated with trypsin, chymotrypsin, and sodium thioglycollate, and the resultant modification of the effect of the hormone on sodium, potassium, and water excretion was studied. These agents, which destroy the antidiuretic-pressor activity of the hormone, also bring about a loss of its natriuretic and kaliuretic effects. The action of Arg8-vasopressin, Phe2-Lys8-vasopressin, and His2-Lys8-vasopressin on sodium, potassium, and water excretion was studied; comparisons were made with the effects of equivalent pressor doses of Lys8-vasopressin. No significant differences between Arg8- and Lys8-vasopressin were obtained. Phe2-Lys8-vasopressin had nearly ten times the antidiuretic effect and four times the natriuretic and kaliuretic effect. Even though His2-Lys8-vasopressin has an antidiuretic effect, it lacks activity with regard to blood pressure or electrolyte excretion.