Functional and structural changes in isolated rabbit liver mitochondria induced by fluorodichloromethane

Fluorodichloromethane caused changes in substrate respiration rates and also in adenosine diphosphate (ADP)-stimulated rates of oxidation of both succinate and glutamate. Active swelling of mitochondria also occurred, but only in the presence of magnesium ion. ADP/O ratios were not significantly affected by the fluorocarbon. State IV respiration was stimulated, and the respiratory control ratio was linearly reduced with increased levels of fluorocarbon when succinate was used as substrate. Glutamate-stimulated respiration was greatly affected by the presence of the halocarbon but contrasted to the succinate responses. Low levels of fluorocarbon stimulated the state IV rate with glutamate whereas higher concentrations inhibited respiration. States III and IV respiration were completely inhibited by levels of 4.7 mg/ml of fluorodichloromethane when the nicotinamide adenine dinucleatide (NADH)-linked substrate was used. The NADH-linked substrate was more sensitive to the fluorocarbon treatment than the flavoprotein-linked substrate. The respiratory control ratio reached 1.0 at one-half the concentration required to elicit the same response with the flavoprotein-linked substrate, which suggested that NADH-dehydrogenase was inhibited. Active swelling of mitochondria occurred in the presence of magnesium and fluorocarbon, greatly exceeding controls, suggesting a loss of structural integrity and osmoregulation capacity. Increased rates of reduction of exogenously added cytochrome c also suggested changes in membrane integrity at higher fluorocarbon site of action of this compound is probably not the NADH-dehydrogenase system but the membrane system per se. Structural changes in the membrane system could account for the reported respiratory inhibition.