Erythrocyte cation-activated adenosine triphosphatases in Duchenne muscular dystrophy

The cation-stimulated adenosine triphosphatase (ATPase) activities of erythrocyte ghosts and erythrocyte ghost plasma membrane fragments of patients with Duchenne muscular dystrophy (DMD) were compared with activities in age-matched normal male controls. DMD Mg++-stimulated ATPase activity was within the normal range. The specific activity of DMD erythrocyte ghost Na+,K+-stimulated, Mg++-dependent ATPase was also normal, and was inhibited by 10(-4) M ouabain to an extent comparable with controls. Ca++-stimulated, Mg++-dependent ATPase activity of DMD erythrocyte ghost plasma membrane fragments, assayed at 0.5 mM free Ca++, was 21% above that in age-matched male controls (n = 22, 2-tailed paired t-test, P less than 0.01). Kinetic studies indicated that the DMD erythrocyte Ca++-stimulated, Mg++-dependent ATPase has greater affinity for MgATP than the enzyme in control erythrocytes.