[Effect of catecholamines on the activity of rabbit kidney microsomal (na+--k+)-activated atpase]

The significance of alpha- and beta-adrenoreceptors and the role of cyclic 3', 5' -AMP in the mechanism of the activation by catecholamines of the microsoma (Na+ - K+)-activated ATP-ase of the rabbits kidneys were investigated. Phentolamine did not obstruct the activating effect of epinephrine in the cortical and medullar layer. Inderal inhibited the reaction of the enzyme in response to epinephrine in the renal cortex and fully prevented any rise of the enzymatic activity in the medullar substances. Isopropylnorpinephrine and cyclic 3',5' -AMP stimulated the (Na+ - K+)-activated ATP-ase in the cortical and medullar layer. An inference is drawn to the effect that the activation of the enzyme occurring under the effect of catecholamines comes as a consequence of a beta-adrenoreceptors stimulation. It is suggested that the cyclic 3',5'-AMP may be directly involved in the mechanism accounting for stimulation by catecholamines of the activity displayed by the microsomal (Na+ - K+)-activated ATP-ase of the rabbits kidneys.