Sodium-potassium-activated adenosine triphosphatase activity as a measure of neuronal membrane characteristics in ethanol-tolerant mice.

(Na+-K+) activated adenosine triphosphatase of mouse synaptosomal membranes is inhibited by high concentrations of ethanol. When membranes were obtained from mice made tolerant to and physically dependent on ethanol by chronic exposure to an ethanol-containing liquid diet, the enzyme was resistant to the inhibitory effects of ethanol. Arrhenius plots of synaptosomal (Na+-K+) activated adenosine triphosphatase from control animals revealed that ethanol added in vitro lowered the transition temperature and altered the Arrhenius activation energies of this enzyme. Enzyme from ethanol-tolerant animals had a lower transition temperature than that from control animals, and ethanol added in vitro had no effect either on transition temperature or on activation energy of enzyme from ethanol-tolerant animals. The occurrence of lowered transition temperature and resistance to ethanol-induced alterations in transition temperature of the enzyme from ethanol-tolerant animals most likely reflects changes in membrane composition. Changes in Arrhenius plots correlated in time with resistance to the inhibitory effects of ethanol on (Na+-K+) activated adenosine triphosphatase activity and the time course of disappearance of these effects was similar to that of the disappearance of functional tolerance to ethanol. The resistance to the effects of ethanol on membrane function may be related to ethanol tolerance evidenced by behavioral and physiological measurements.