Ouabain-Like and Non-Ouabain-Like Factors in Plasma of Patients with Essential Hypertension

Circulating inhibitor of Na+,K+-ATPase and ouabain-like immunoreactivity were studied in patients with essential hypertension. In the plasma of patients, two types of Na+,K+-ATPase inhibitors (ouabain-like and non-ouabain-like inhibitors) and ouabain-like immunoreactivity were detected. Ouabain-like inhibitor was clearly detected at a low KCl concentration (0.1 mM) in the assay buffer, and non-ouabain-like inhibitor was detected at a high KCl concentration (10 mM). The plasma level of ouabain-like inhibitor correlated significantly with that of ouabain-like immunoreactivity (p less than 0.001) and with a mean blood pressure (p less than 0.01). The plasma level of non-ouabain-like inhibitor was not correlated with the levels of either ouabain-like immunoreactivity or mean blood pressure. The level of plasma ouabain-like inhibitor did not correlate with that of plasma non-ouabain like inhibitor. Both ouabain-like inhibitor and ouabain-like immunoreactivity in the plasma of patients with essential hypertension were significantly higher than those in normotensive subjects, but the plasma level of non-ouabain-like inhibitor in patients with essential hypertension was not higher than that in normotensive subjects. These results suggest that the plasma from patients with essential hypertension contains ouabain-like factor(s) which is important to maintain the high blood pressure.