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

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 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.