[Availability of Mg2+, Na+, and K+-ATPase in the nuclei of the skeletal muscles of rabbits normally and during experimental muscular dystrophy].

A comparative study was carried out in the properties of ATPase system of the skeletal muscle nuclei in the rabbits in norm and with experimental muscular dystrophy conditioned by E-avitaminosis. It is shown that in the system, containing 1.5 mM of MgCl2, ATPase system of the nuclei is activated by sodium and potassium ions. In norm maximum activation is observed with their presence in the medium, the concentration being 80 and 70 mM, respectively. With experimental muscular dystrophy maximum activating concentrations decrease and are equal for both cations - 30 mM. Activation of the enzymatic system by these ions is specific because the introduction of equimolar quantities of cholin-chloride or lithium, cesium ions instead of sodium ions into the incubation medium evokes no activation of the ATPase system of the rabbit skeletal muscles both in norm and with experimental muscular dystrophy. A simultaneous presence of sodium and potassium ions in optimum concentrations in the incubation medium makes for an increase of ATPase activity to the same extent as the presence of one of these cations. Oubain, a specific inhibitor of Mg2+, Na+, K+- ATPase, taken in the concentrations of 10(-4) and 10(-3) M did not decrease the intensity of ATP hydrolysis and its activation conditioned by the presence of sodium or potassium. A conclusion is made that Mg2+, Na+, K+-ATPase taking part in the work of "sodium pump" is absent in the nuclei of skeletal muscles.