Effect of noradrenaline and vanadium on Na+K+-activated ATPase in rat cerebral cortex synaptosomal preparation

The effect of l-noradrenaline and vanadate on the activity of Na+K+-activated ATPase was studied on synaptosomal brain cortex preparation. Using neutron activation analysis it was found that the rat cerebral cortex synaptosomal preparation contains 0.16 microM vanadium. The concentration of vanadium needed to reduce enzyme activity by 50% proved to be 2 x 10(-6) M. Evidence has been provided that the increase by noradrenaline of enzyme activity in synaptosomal preparation depends on the presence of an inhibitory contaminant in commercial ATP preparations. In homogenate, however, noradrenaline was able to enhance enzyme activity even when vanadium-free ATP was used. This fact indicates that noradrenaline removes the inhibitory effect of cytoplasmic factor thereby stimulating enzyme activity.