The Renin-Angiotensin System

Abstract

Since the discovery of renin 80 years ago, there have been remarkable advances in our understanding of the renin-angiotensin system. The system as it is known today is summarized in Figure 1. Angiotensin III, the active component of the system, has several important physiological actions. The first of these to be identified was its pressor action, and for many years it was felt that the sole function of the renin-angiotensin system was regula­ tion of blood pressure. A new dimension was added in 1960 with the discovery that angiotensin II stimulates the secretion of aldosterone and is therefore in a position to exert important effects on salt and water balance. Several additional actions of angiotensin II were then discovered. It was found that the peptide can increase the secretion of catecholamines from the adrenal and facilitate adrenergic transmission. It also acts directly on the brain to increase blood pressure via sympathetic and parasympathetic path­ ways, to produce thirst, and to stimulate the secretion of vasopressin and ACTH. Through these actions, the renin-angiotensin system plays an im­ portant role in the regulation of blood pressure and of the volume and composition of the extracellular fluid. Major advances have also been made in our understanding of other aspects of the renin-angiotensin system. It has become clear that the hep­ tapeptide metabolite of angiotensin II, [des-Aspl] angiotensin II (angio-