Renal Dysfunction, Rather Than Nonrenal Vascular Dysfunction, Mediates Salt-Induced Hypertension.

Abstract

Chronic excess salt intake increases the risk for hypertension and moderation of salt intake is an important strategy for prevention of cardiovascular and kidney disease, especially in salt-sensitive subjects. Although short-term blood pressure (BP) responses to high salt intake over several days are highly variable, chronic high salt intake worsens BP salt-sensitivity. Aging, diabetes, hypertension, and various acquired and genetic kidney disorders also exacerbate salt-sensitivity of BP. Kidney dysfunction, characterized by impaired pressure natriuresis, has been demonstrated in all forms of experimental and human genetic or acquired salt-sensitive hypertension studied thus far. Abnormalities of kidney function that directly or indirectly increase NaCl reabsorption, decrease glomerular capillary filtration coefficient, or cause nephron injury/loss exacerbate BP salt-sensitivity. In most cases, salt-sensitive hypertension is effectively treated with drugs that increase glomerular filtration rate or reduce renal NaCl reabsorption (e.g. diuretics, renin-angiotensin-aldosterone system blockers). Increased vascular resistance may occur concomitantly or secondarily to kidney dysfunction and increased BP in salt-sensitive hypertension. However, primary increases in <i>non-renal</i> vascular resistance have not been shown to cause salt-sensitive hypertension or long-term changes in BP in the absence of impaired renal-pressure natriuresis. The mechanisms responsible for increased total peripheral resistance (TPR) during high salt intake in salt-sensitive subjects are not fully understood but likely involve pressure-dependent and/or flow-dependent autoregulation in peripheral tissues as well as neurohormonal factors that occur concomitantly with kidney dysfunction. Physiological studies have demonstrated that increased BP almost invariably initiates secondary pressure-dependent functional and structural vascular changes that increase TPR.