Pattern of Na-K-ATPase inhibitors in plasma and urine of hypertensive patients: a preliminary report.

The pattern of endogenous Na-K-ATPase inhibitors in plasma and urine from patients with essential hypertension and normal controls was established by sequential Amicon ultrafiltration through membranes with molecular weight cut-offs of 50 K daltons, 30 K daltons and 1 K daltons, followed by C18 Sep-Pak cartridge separation of the 1 K filtrate. Significantly increased Na-K-ATPase inhibitory activity in the hypertensive population was found in a high molecular weight (30-50 K daltons) urine fraction, one low molecular weight (less than 1 K daltons) urine fraction and two low molecular weight plasma fractions. Preliminary evidence is presented to suggest that large molecular weight plasma fractions may contain a "masked" Na-K-ATPase inhibitor, in either carrier or precursor form.