title: Abnormal Na+-K+ ATPase kinetics in a subset of essential hypertensive patients.
abstract: We have performed a kinetic analysis of the interaction of Na+-K+ ATPase with internal Na+ in erythrocytes of 30 normotensive controls and 72 essential hypertensive patients. Neither the maximal rate of ouabain-sensitive sodium efflux (Vmax) nor the internal Na+ content required for half-maximal stimulation (K50%) were significantly different between normotensive and hypertensive patients. Nevertheless, using the 95% confidence limits of the K50% in the normotensive group as a cut-off point, 13 (18.06%) essential hypertensive patients exhibited increased values of this parameter (29.16 +/- 4.31 mmol l-1 cells) revealing decreased affinity of Na+-K+ ATPase for internal Na+ (Pump-hypertensives). The Vmax was also higher in the Pump '-' subset (14.08 +/- 4.85 mmol (1 cells h)-1 vs. 6.92 +/- 1.80; P = 0.0002) and 10 of these 13 hypertensives exhibited a Vmax above the upper end limit of 10.5 mmol (1 cells h)-1, suggesting a compensatory effect. No differences were observed between the Pump '-' subset and the remaining 59 hypertensives without Na+-K+ pump abnormality when basal erythrocyte Na+ content and clinical parameters of hypertension were examined. Decreased apparent affinity of Na+-K+ pump for internal Na+ present in 9-27% of essential hypertensives may be implicated in pathogenetic mechanisms of hypertension.
authors.affiliation: Servicio de Medicina Interna General, Hospital Clínic i Provincial, Barcelona, Spain.
authors.forename: A
authors.initials: A
authors.lastname: de la Sierra
authors.forename: A
authors.initials: A
authors.lastname: Coca
authors.forename: M T
authors.initials: MT
authors.lastname: Aguilera
authors.forename: A
authors.initials: A
authors.lastname: Urbano
mesh_terms: D000328:Adult; D000368:Aged; D004912:Erythrocytes / Q000201:enzymology; D005260:Female; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000145:classification / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D015221:Potassium Channels / Q000378:metabolism; D015222:Sodium Channels / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000097:blood*
chemical_list: D015221:Potassium Channels; D015222:Sodium Channels; D000254:Sodium-Potassium-Exchanging ATPase