Fate and excretion of the pressor activity of vasopressin in rats

The fate of the antidiuretic activity of vasopressin has been investigated in experiments in vivo (Burn & Singh Grewal, 1951; Heller, 1952, 1953; Ginsburg & Heller, 1953; Dicker, 1954; Dicker & Greenbaum, 1954) and in experiments in vitro (Heller & Urban, 1935; Birnie, 1953; Dicker & Greenbaum, 1956). The antidiuretic activity of vasopressin appears to be inactivated by both liver and kidneys though the manner in which the inactivation takes place is still not clear. As for the metabolism of the pressor activity of vasopressin, little is known about its fate in the body beyond the fact that the pressor activity of post-pituitary gland extracts appears to be less stable than the antidiuretic activity (Heller, 1939). Since vasopressin has been synthesized there can be no doubt that both activities belong to the same octapeptide molecule. According to van Dyke (1955) the pharmacological activities of the vasopressin are abolished by cleavage of the disulphide bond. As, however, the two activities of vasopressin are so different, there is a possibility that the metabolism and the rate of excretion of the pressor activity are different from those of the antidiuretic activity. The present investigation is a contribution to this problem.