DIAZACHOLESTEROL EFFECT UPON MEMBRANE ATPASE

ATPase activity of erythrocyte ghost preparations and of a muscle membrane fraction (sarcoplasmic reticulum) from untreated rabbits was inhibited by the cardiac glycoside, ouabain. Sustained treatment of animals with 20,25 diazacholesterol, reported by Winer et al. (1965) to induce myotonia, changed the character of the ATPase activity of identical preparations such that a stimulation of the catalytic rate was effected by the presence o ouabain in the incubation mixture. We have earlier suggested that the ATPase response to ouabain is a reflection of the conformation of the enzyme which it derives in part from its association with the membrane. The present findings accord with the common supposition that myotonia involves aberrant transport phenomena and appears to indicate that diazacholesterol administration directly affects the membrane transport system. © 1968.