ERYTHROCYTE NA-ATPASE PROPERTIES AND ADENYLATE ENERGY-CHARGE IN NORMOTENSIVES AND IN ESSENTIAL HYPERTENSIVES(,K+)

The activity and some kinetic properties of RBC Na+,K+-ATPase (EC 3.6. 1.37) were investigated in essential hypertensives (EH; 40 subjects) a nd normotensives (NT; 20 subjects). A decrease in ouabain-sensitive Rb -86 uptake as well as ouabain-sensitive ATPase activity was found in E H. [Na+](i) and [K+](i) of EH did not show any statistical difference from NT. Na+,K+-ATPase showed a reduced Mg2+ activation and the appare nt K-m value for Mg2+ was 2-fold increased in the EH group. The influe nce of temperature on the Na+,K+-ATPase showed a reduced modulation an d a minor activity peak at 37 degrees C in the patients, consequently the calculated activation energy of the enzyme was increased at temper atures lower than 40 degrees C. Increased RBC adenylate energy charge (EC) was observed in EH when compared with NT. A negative correlation between EC and total Na+,K+-ATPase activity was found when all subject s were compared and also in both groups, showing a possible pump invol vement in the regulation of the RBC metabolic flux in EH. These data p rovide evidence about some modifications in active Na+,K+ transport an d in EC in RBC which allows a further characterization of membrane cat ion fluxes in EH.