The effects of diphenyleneiodonium and of 2,4-dichlorodiphenyleneiodonium on mitochondrial reactions. Mechanism of the inhibition of oxygen uptake as a consequence of the catalysis of the chloride/hydroxyl-ion exchange.
1. Increasing the substrate concentration only decreased the inhibition of mitochondrial oxidations by diphenyleneiodonium or by 2,4-dichlorophenyleneiodonium by a small amount. 2. Diphenyleneiodonium and 2,4-dichlorodiphenyleneiodonium lowered the amounts of succinate, citrate and glutamate accumulated in the matrix of mitochondria in the presence of Cl-, but not in its absences. 2,4-Dichlorodiphenyleneiodonium decreased the accumulation of substrates by mitochondria oxidizing glycerol 3-phosphate. 3. Diphenyleneiodonium caused an alkalinization of the medium with an anaerobic suspension of mitochondria, which was only partly reversed by Triton X-100. 4. The rate of proton extrusion by mitochondria oxidizing succinate was not altered by diphenyleneiodonium or by 2,4-dichlorodiphenyleneiodium, although the rate of decay of proton pulses was increased. 5. 2,4-Dichlorodiphenyleneiodonium shifted the pH optimum for succinate oxidation by intact mitochondria from pH 7.2 to 8.0, whereas there was no effect on that of freeze-thawed mitochondria, which was pH 8.0. 6. The concentration of 2,4-dichlorophenyleneiodonium required to inhibit respiration by 50% is less the higher the absolute rate of oxygen uptake. 7. EDTA, but not EGTA [ethanedioxybis(ethylamine)-tetra-acetic acid] increased the inhibition of respiration by diphenyleneiodonium, 2,4-dichlorodiphenyleneiodonium and by tri-n-propyltin. 8. It is concluded that diphenyleneiodonium and 2,4-dichlorodiphenyleneiodonium limit respiration in Cl--containing medium by causing an acidification of the matrix, and that there are pH-sensitive sites in the respiratory chain between NADH and succinate, and between succinate and cytochrome c.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism; D002951:Citrates / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D005971:Glutamates / Q000378:metabolism; D006843:Hydrocarbons, Chlorinated / Q000494:pharmacology*; D006847:Hydrocarbons, Iodinated / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D006878:Hydroxides / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D008933:Mitochondrial Swelling / Q000187:drug effects; D009861:Onium Compounds / Q000037:antagonists & inhibitors / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects*; D051381:Rats; D013386:Succinates / Q000378:metabolism
D002712:Chlorides; D002951:Citrates; D005971:Glutamates; D006843:Hydrocarbons, Chlorinated; D006847:Hydrocarbons, Iodinated; D006878:Hydroxides; D009861:Onium Compounds; D013386:Succinates; C012892:2,4-dichlorodiphenyleneiodonium; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D004492:Edetic Acid; D008274:Magnesium