Ca2+—ATPase and Na+‐K+–ATPase content in skeletal muscle from malignant hyperthermia patients

The purpose of this study was to determine the concentration of Ca(2+)-ATPase and Na(+)-K(+)-ATPase in biopsies from vastus lateralis muscle of 24 patients, who underwent a diagnostic contracture test for susceptibility to malignant hyperthermia (MH). Ca(2+)-ATPase was quantified as the Ca(2+)-dependent 32P incorporation in whole muscle homogenates. Na(+)-K(+)-ATPase was quantified as the [3H]ouabain-binding capacity in intact muscle samples. These methods avoid isolation of membranes, a procedure that may influence the results due to interindividual variation in recovery. The results show that both enzymes can be determined in (frozen) muscle biopsies weighing 50 mg. Neither the concentration of Ca(2+)-ATPase nor that of Na(+)-K(+)-ATPase differed in biopsies from subjects diagnosed as susceptible (MHS) or nonsusceptible (MHN) to MH. Our data support the view that changes in the concentration of Ca(2+)-ATPase and/or Na(+)-K(+)-ATPase do not play a primary role in the pathogenesis of MH.