Sodium-sensitive
hypertension is thought to be dependent on primary alterations in renal tubular
sodium reabsorption. The major apical plasma membrane Na(+) transporters include the proximal tubular
Na(+)-H(+) exchanger, the thick ascending limb Na(+)-K(+)-2Cl(-) cotransport system, the distal tubular
Na(+)-Cl(-) cotransporter, and the collecting duct
epithelial sodium channel (ENaC). This article explores the role of each transporter in the pathogenesis of
hypertension. Although the contribution of the proximal tubule
Na(+)-H(+) exchanger is not yet defined completely, more convincing data have been generated about the importance of the Na(+)-K(+)-2Cl(-). Indeed at least 2 forms of
hypertension appear to be related to the up-regulation of the transporter: the so-called programmed
hypertension induced by
low-protein diet during pregnancy and the early phase of
hypertension in the Milan strain of rats. With respect to the
Na(+)-Cl(-) cotransporter this may be overactive caused by inactivating mutation of WNK4 as in the
Gordon syndrome, although it is the main actor for the maintenance phase of the
hypertension found in the Milan strain of rats. Finally, the contribution of the ENaC has been established clearly; indeed, in the
Liddle syndrome the mutation of the ENaC gene leads to a longer retention of the channel on the cell surface of collecting duct principal cells, thus inducing stronger
sodium reabsorption along this segment. All these examples clearly indicate that renal
sodium transporters may be responsible for various types of
sodium-sensitive
hypertension.