Plasma membrane Ca(2+)-ATPase sulfhydryl modifications: implication for oxidized red cell.

A common perturbation found in cells under oxidative stress is alteration in cellular Ca2+ homeostasis. In order to understand the effects of such oxidative damage, human red cell plasma membrane Ca(2+)-ATPase (PMCA) was studied by measuring PMCA activity, both in the presence and absence of calmodulin (CaM), following treatment with sulfhydryl agents, N-ethylmaleimide, iodoacetate and diamide. PMCA activity of washed red cell membrane was measured by coupling with pyruvate kinase, using phosphoenolpyruvate as substrate, and lactate dehydrogenase to convert pyruvate to lactate employing beta-NADH as co-factor.