Sensitivity and reversibility of Ca-dependent inhibition of the (Na+ + K+)-ATPase of human red blood cells |
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Affiliation: | 1. Department of Neurology, Mayo Clinic, Scottsdale, AZ, United States;2. Division of General Internal Medicine, Mayo Clinic, Rochester, MN, United States |
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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 μM to approx. 1 μM. 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 destroyed its effect on the (Na+ + K+)-ATPase, but did not impair its stimulation of the Ca2+-ATPase. |
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