Action of propranolol on mitochondrial proton fluxes.

The action of propranolol, a Beta-blocking adrenergic agent, on mitochondrial proton fluxes in nonenergized and energized conditions has been studied. 1. The drug inhibited the actions of valinomycin, higericin and FCCP on the inner mitochondrial membrane. 2. It decreased the rate and extent of active energized proton expulsion and passive collapse of the proton gradient so formed. 3. Propranolol was able to increase the permeation of chloride ion through the inner mitochondrial membrane in nonenergized and energized conditions. 4. The drug inhibited mitochondrial contraction but stimulated swelling in various conditions. It is suggested that propranolol is is able to change the proton and chloride permeabilities of mitochondria by perturbing the structure of inner membrane phospholipids, thus enlarging the water-lipid interface.