Regulation of (Na+, K+) adenosinetriphosphatase of nerve ending membranes: action of norepinephrine and a soluble factor.

Norepinephrine added in vitro to nerve ending membranes from rat cerebral cortex stimulates the activity of (Na+, K+) adenosinetriphosphatase (ATPase) only in the presence of the soluble brain fraction. In its absence norepinephrine inhibits the enzyme. (Mg2+)ATPase also showed stimulation by norepinephrine in the presence of the soluble fraction, but of lesser magnitude. The activation of (Na+, K+)ATPase by norepinephrine is not reproduced by cyclic AMP and is not antagonized by either alpha- or beta-adrenergic blocking agents. These results suggest that the stimulation caused by norepinephrine is a direct effect on the enzyme and is not mediated by cyclic AMP or adrenergic receptors.