The Role of Na,K-ATPase Inhibitor on Pressor Responsiveness in Patients With Benign Essential Hypertension

To clarify the role of Na,K-ATPase inhibitor in the enhanced pressor response to infused noradrenaline (NA-R) in patients with benign essential hypertension (EHT), NA-R, plasma noradrenaline concentration (PNA), and blood ionized calcium (Ca2+) were investigated before and after intravenous injection of ouabain in 15 normotensive subjects (NT) and 13 EHT. NA-R was enhanced by ouabain in both NT and EHT. The augmentation of NA-R following ouabain injection (delta NA-R) and % delta NA-R were significantly lower in EHT than in NT. Following ouabain injection, no significant change in PNA and blood Ca2+ was observed in both NT and EHT. NA-R negatively correlated with PNA and blood Ca2+, which were estimated just prior to noradrenaline infusion, before ouabain injection as well as after. After ouabain, the regression line between NA-R and PNA or blood Ca2+ shifted toward higher NA-R level in NT, unlike in EHT. These results suggest that an exogenous Na,K-ATPase inhibitor brings about a blunted enhancement of NA-R in EHT consistent with the presence of an endogenous Na,K-ATPase inhibitor in EHT.