Relation of sodium-potassium adenosine triphosphatase inhibitor to sympathetic nervous system during salt-loading in essential hypertension.

The present study was designed to assess if the release of Na-K ATPase inhibitor (NKAI) after salt-loading is related to sympathetic nervous system in essential hypertension. Thirteen patients with essential hypertension were studied during low-salt diet (2 g/day) and then high-salt diet (20 g/day) for each 7-days period. Mean blood pressure (MBP), body weight, Na:K ratio in red blood cell (R-Na/K), plasma norepinephrine (PNE) and NKAI were measured on the last day of each period. NKAI was determined by the degree of the inhibition of dog kidney Na-K ATPase activity by deproteinized plasma. Patients were classified as "salt-sensitive" (SS) or "nonsalt-sensitive" (NSS) group by the MBP responses to salt-loading. With the high-salt diet, SS group showed more body weight gain, greater increase in R-Na/K and NKAI (SS; 8.0 +/- 1.0%, NSS; 2.4 +/- 0.8%, P less than 0.01) than NSS group. PNE showed no changes in SS group and decreased in NSS group (P less than 0.05). The increase of MBP was highly correlated with the rise of NKAI (r = 0.76, P less than 0.01). Moreover, the increase of NKAI was also significantly correlated with the changes of PNE (r = 0.62, P less than 0.05). These results suggest that the greater increase in blood pressure by salt-loading in SS patients can be attributed to the increase of NKAI, which might regulate the sympathetic nervous system as a result of increased intracellular sodium.