Interaction between propranolol and electron donors in altering the calcium ion‐dependent potassium ion‐permeability of the human red blood cell membrane

Both propranolol and the electron donors ascorbate plus phenazine methosulfate increase the K+-permeability of the red blood cell membrane. The present investigation examined whether these effects were additive. Contrary to expectations, propranolol added after electron donors sharply inhibited the K+ (86Rb) efflux induced by such donors, without forming new K+ channels analogous to those induced by propranolol in intact red blood cells. The inhibitory effect of propranolol may be due to generalized disturbances of membrane structures necessary for the functioning of the K+ channels organized in the presence of reducing agents. In contrast, the electron donors added after propranolol caused a further stimulation of the 86Rb loss from the propranolol-treated red cells. The combined effect of these drugs therefore depends on the order of their addition. The possible mechanism of their interaction is briefly discussed.