Interactions between arterial pressure and sodium excretion.

Recent developments have led to renewed interest in the mechanisms that mediate the changes in sodium excretion in response to changes in arterial pressure, a phenomenon termed pressure-natriuresis. Pressure-natriuresis occurs in the absence of changes in filtered load and thus, the changes in sodium excretion are caused by changes in net tubular sodium reabsorption. Both proximal and distal nephron segments have been implicated as the sites of altered reabsorption. The specific mechanism responsible for pressure-natriuresis remains unresolved. One proposal suggests that changes in renal interstitial fluid pressure which may be due, in part, to a less efficient autoregulation of the renal medullary circulation than of the cortex, alter sodium reabsorption. Alternatively, recent studies indicate that increases in arterial pressure increase endothelial nitric oxide formation which inhibits sodium reabsorption via direct effects on the tubules as well as hemodynamically mediated effects.