Ca 2+-activated membrane ATPase: Selective inhibition by ruthenium red

Abstract

1. 1. Ca 2+-ATPase, (Na +-K +)-ATPase and Mg 2+-ATPase activities were determined in isolated red blood cell membranes. 2. 2. The hexavalent dye, ruthenium red, produced concentration-dependent inhibition of Ca 2+-ATPase ( I 50 ≅ 10 −5 M ) without significantly affecting (Na +-K +)-ATPase or Mg 2+-ATPase. 3. 3. We suggest that ruthenium red may be a useful tool for selective inhibition of Ca 2+ transport and/or Ca 2+-ATPase.