Some Effects of Decenylsuccinic Acid on Isolated Corn Mitochondria

The effects of decenylsuccinic acid on the swelling and respiratory capacities of mitochondria isolated from etiolated corn ( Zea mays L., Wf9 × M14) shoots were studied. Decenylsuccinic acid (0.1 mM to 1.0 mM) inhibited the oxidation of succinate and malate-pyruvate, stimulated the oxidation of reduced nicotinamide adenine dinucleotide, and uncoupled phosphorylation. The swelling of isolated corn mitochondria, as determined by percentage of transmittance changes, was stimulated by decenylsuccinic acid in potassium chloride reaction media and in sucrose reaction media without bovine serum albumin. In a diaphorase (2, 6-dichlorophenolindophenol as acceptor) reaction with intact mitochondria, only the dehydrogenation rate of malate was reduced by the addition of decenylsuccinic acid. The dehydrogenation of reduced nicotinamide adenine dinucleotide or of succinate was either not affected or was stimulated depending on the diaphorase reaction medium. The oxygen uptake of mitochondria oxidizing N, N, N′, N′-tetramethyl- p -phenylenediamine diHCl and ascorbate was inhibited at decenylsuccinic acid concentrations greater than 0.5 mM. The results presented lead to the hypothesis that the primary effect of decenylsuccinic acid on isolated corn mitochondria is on the physical properties of the membranes and that decenylsuccinic acid-affected stimulation or inhibition of respiration results from the physical disruption of the membrane. These results appear to be consistent with those previously reported in whole plant studies.