The renin-angiotensin system and sodium homeostasis

The available evidence suggests that angiotensin plays an important role in sodium homeostasis not only via aldosterone release but also through control of the renal circulation, and thereby renal sodium handling. Perhaps this intrarenal action is the renin-angiotensin system's original, primitive function. Through its vascular action, angiotensin has an important influence on glomerular filtration and tubular reabsorption. Angiotensin almost certainly also has an additional intraglomerular action. More circumstantial, but compelling, evidence suggests that angiotensin contributes to the renal response in a host of conditions characterized by renal vasoconstriction, a reduction in filtration rate, and sodium retention, including heart failure, cirrhosis of the liver, complications of pregnancy, the renal response to trauma and shock, and in selected patients with essential and secondary hypertension. Pharmacologic interruption of the renin-angiotensin system is proving useful not only for blood pressure control in patients with hypertension but also because of its influence on the kidney in some or all of these conditions--at least in part attributable to restoration of more normal renal sodium handling.