Abstract
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<0.01) than NSS group. PNE showed no changes in SS group and decreased in NSS group (P<0.05). The increase of MBP was highly correlated with the rise of NKAI (r=0.76, P<0.01). Moreover, the increase of NKAI was also significantly correlated with the changes of PNE (r=0.62, P<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.
