title: Sensitivity and reversibility of Ca-dependent inhibition of the (Na+ + K+)-ATPase of human red blood cells.
abstract: The sensitivity of the (Na+ + K+)-ATPase to inhibition by Ca was increased 30-fold by a partially purified extract of human red cell hemolysate. The hemolysate fraction reduced the concentration of free Ca required for 50% inhibition from 30 microM to approx. 1 microM. Ca-dependent inhibition of the (Na+ + K+)-ATPase in the presence and absence of the hemolysate fraction was completely reversible. The hemolysate fraction also stimulated the Ca2+-ATPase and increased its affinity for Ca. In the presence of the hemolysate fraction, the concentration of free Ca that inhibited the (Na+ + K+)-ATPase by 50% was similar to that which half-maximally stimulated the Ca2+-ATPase. Boiling the fraction destoryed its effect on the (Na+ + K+)-ATPase, but did not impair its stimulation of the Ca2+-ATPase.
authors.forename: D R
authors.initials: DR
authors.lastname: Yingst
authors.forename: P M
authors.initials: PM
authors.lastname: Polasek
mesh_terms: D002118:Calcium / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000097:blood; D004912:Erythrocytes / Q000201:enzymology*; D006461:Hemolysis; D006801:Humans; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000097:blood
chemical_list: D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium