THE PRESSOR EFFECT OF THE ANTIDIURETIC PRINCIPLE OF THE POSTERIOR PITUITARY IN ORTHOSTATIC HYPOTENSION 1

Abstract

In 3 patients with diffuse autonomic nervous system disease manifested by orthostatic hypotension, anhidrosis and impotence, the antidiuretic principle of the posterior pituitary produced a marked rise in arterial pressure. In contrast, it was confirmed that in normal subjects, posterior pituitary extracts had no significant effect on arterial pressure. In the patients with orthostatic hypotension, intravenous infusion of 1 milliunit per minute of highly purified vasopressin resulted in a 20-30 mm Hg rise in arterial pressure. In each patient, arterial pressures greater than 170/100 mm Hg were produced by a single intravenous injection of 1 unit of purified vasopressin, or by continuous infusion of 10 milliunits per minute. The increase in arterial pressure was related to a rise in the total systemic vascular resistance and was not due to a change in the cardiac output. In addition, vasopressin administration resulted in a rise in calculated pulmonary and renal vascular resistances. Increased sensitivity to the pressor activity of vasopressin in patients with orthostatic hypotension may be related to increased reactivity of vascular smooth muscle and to absence of normal vasodepressor reflexes. This effect was observed with dosages that approach the physiologic range of andogenous antidiuretic hormone secretion.