Inhibition of an oligomycin-sensitive ATPase by cationic dyes, some of which are atypical uncouplers of intact mitochondria

Abstract

The inhibition of an oligomycin sensitive ATPase prepared from bovine heart submitochondrial particles ( J. A. Berden and M. M. Voorn-Brouwer, 1978, Biochim. Biophys. Acta 501, 424–439) by a number of cationic dyes has been compared in order to develop a structure-function relationship. Two generalizations emerge from this comparison. First, the most effective dyes have net positive charge at neutral pH; and second, those dyes containing alkyl substituted secondary and tertiary amino groups are more effective than analogs with primary aromatic amino groups. Some of the cationic dyes exhibit uncoupling activity when added to intact rat liver mitochondria, stimulating both State 4 respiration and the latent ATPase activity. The order of effectiveness and concentrations for maximal stimulation of respiration are: coriphosphine (0.3 μ m), Nile blue A (0.5 μ m), pyronin Y (0.8 μ m), and acridine orange (10 μ m). Atypically, oligomycin inhibits the stimulation of respiration by these cationic acid uncouplers. The order of effectiveness and concentrations for maximal stimulation of the latent ATPase are: Nile blue A (2 μ m), pyronin Y (8 μ m), acridine orange (25 μ m), and coriphosphine (75 μ m). At concentrations greater than those shown for maximal stimulation, the uncoupling dyes inhibited respiration and the latent ATPase. The cationic dyes tested that were not uncouplers are inhibitors of respiration and the latent ATPase of intact mitochondria at all concentrations tested.