Change of mitochondrial buffering capacity induced by propranolol.

Propranolol is able to increase the amount of the titratable groups of mitochondrial membranes. This effect occurs with sonicated particles and with liposomes, too. The phenomenon is only seen in the presence of salt solutions, not in sucrose. Propranolol increases the fluorescence of anilino-naphthalene sulphonate (ANS) in mitochondrial suspensions. The increase is counteracted by increasing concentrations of potassium chloride. It is suggested that the increase of the titratable groups results from a decrease of the aggregation of the phospholipids of the membranes. At the same time the environment of the bound ANS molecules is more hydrophobic in sucrose than in potassium chloride. The amount of the buffering groups and the hydrophilicity are in direct and the amount of the buffering groups and the fluorescence of ANS in inverse correlation.