Effect of Upright Posture and Isoproterenol Infusion on Cyclic Adenosine Monophosphate Excretion in Control Subjects and Patients with Labile Hypertension.1

Abstract

Labile hypertension is often characterized by β-adrenergic hyperactivity accompanied by an increased responsiveness of renin to upright posture. β-adrenergic receptors are related to the cyclic AMP generating enzyme, adenylate cyclase. In order to evaluate a possible relationship between cyclic AMP, the circulatory hyperactivity, and renin hyperresponsiveness, urinary excretion of cyclic AMP was measured by radioimmunoassay in 12 control subjects and 14 patients with labile hyperkinetic hypertension. Four-hr urines were collected at the same time of the day in recumbent and upright positions and after isoproterenol stimulation. The excretion of cyclic AMP in upright posture decreased in control subjects and increased significantly in labile hypertensive patients. Similar response was observed after isoproterenol infusion in both groups of subjects.