title: Measurement of endogenous Na+,K+-ATPase inhibitors in human plasma and urine using high-performance liquid chromatography.
abstract: This study was undertaken to assess endogenous Na+,K+-ATPase inhibitors in both plasma and urine in the same subjects. Samples were chromatographed on reverse-phase HPLC using an acetonitrile gradient and the eluent screened using Na+,K+-ATPase inhibition and cross-reaction with anti-digoxin antibodies. The donors were divided into inhibiting and non-inhibiting subjects using a previously described method, plasma action on ouabain binding and on Na+,K+-ATPase activity. Three Na+,K+-ATPase inhibitors (1P, 2P and 3P) were detectable in plasma; the antibodies cross-reaction of the peaks 2P and 3P were larger than that of peak 1P. The peaks 2P and 3P were significantly higher in inhibiting subjects as compared to non-inhibiting subjects. The 24-h urine is resolved into two peaks inhibiting Na+,K+-ATPase activity (1U and 2U). Peak 2U cross-reacted with anti-digoxin antibodies to a greater extent than peak 1U and is significantly larger in inhibiting subjects in terms of Na+,K+-ATPase inhibition. These data support the heterogeneity of human Na+,K+-ATPase inhibitor in both plasma and urine.
mesh_terms: D000906:Antibodies / Q000276:immunology; D002851:Chromatography, High Pressure Liquid; D004077:Digoxin / Q000276:immunology; D000939:Epitopes / Q000276:immunology; D006801:Humans; D006973:Hypertension / Q000097:blood* / Q000652:urine; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*
chemical_list: D000906:Antibodies; D000939:Epitopes; D004077:Digoxin; D000254:Sodium-Potassium-Exchanging ATPase