Effect of isopropyl-3-chlorocarbanilate and isopropyl-3-chlorohydroxycarbanilate analogs upon oxidative phosphorylation in plant mitochondria

The effects of the herbicide, isopropyl-3-chlorocarbanilate, and its hydroxylated metabolites, isopropyl-5-chloro-2-hydroxycarbanilate and isopropyl-3-chloro-4-hydroxycarbanilate, upon NADH oxidation, P_i uptake or release, and ATP formation were studied in corn mitochondria. The results indicated that 0.1 mM isopropyl-3-chlorocarbanilate and the 2-hydroxy-metabolite inhibited NADH oxidation by 30% whereas only the 2-hydroxy-metabolite inhibited NADH-linked ATP formation (85–100%). Dinitrophenol and the 2-hydroxy-metabolite exerted similar effects upon respiration, phosphorylation, and ATPase activity. The 4-hydroxy-metabolite (0.1 mM) exerted no effect upon respiration, phosphorylation, or ATPase activity. The β-O-glucoside conjugates of the hydroxymetabolities of isopropyl-3-chlorocarbanilate did not inhibit NADH-linked respiration or phosphorylation at 0.1 mM concentrations. Comparative studies with corn, cucumber, and soybean mitochondria indicated that the parent herbicide and its metabolites affected respiration and phosphorylation activities in a similar manner.