Abstract:
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 Na+, 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 erythrocyte by a direct effect which does not involve protein phosphorylation.