Cyclic AMP increase the Na+ permeability of the avian erythrocyte membrane by a process which does not involve protein phosphorylation.

Preparations of avian erythrocyte plasma membranes have been made which are in the form of sealed vesicles. Using these preparations the permeability of the membranes to N+, K+, Mg2+ and Ca2+ was measured. Monobutyryl cyclic AMP and cyclic AMP increased the permeability to Na+ and Ca+ under conditions where no protein phosphorylation could occur. The only effect of phosphorylation of membrane proteins was to reduce Ca+ permeability. It is thus concluded that cyclic AMP increases Na+ permeability in the avian erythroycte by a direct effect which does not involve protein phosphorylation.