[Mechanism of the activating action of noradrenaline on rat cerebral cortex Na, K-ATPase]

Effect of noradrenaline on kinetics of Na, K-ATPase activation in rat brain cortex was studied using ATP as a substrate and Na+ or K+ ions as cofactors. Noradrenaline (5 x 10(-5) M) increased the activating effect of ATP and Mg2+ as well as that of Na+ and K+. In presence of ATP and Mg2+ the hormone activated ATPase by the mixed type, and in response to Na+, K+ addition--by the non-competitive type. Noradrenaline appears to cause the conformational alterations in Na, K-ATPase molecule, which change the kinetics of the enzyme activation by ATP and the ions.