Effect of diuretics on oxidative phosphorylation of dog kidney mitochondria

An effect of diuretics on cellular metabolism has been shown. In order to examine further the direct effect of diuretics on renal mitochondria, their effect on isolated cortical (C) and outer medullary (OM) mitochondrial respiration was examined. Oxygen consumption rate (QO2) was measured in a Gilson oxygraph utilizing either glutamate-malate or succinate as substrate. QO2, expressed in nanoatoms of O2 per milligram of protein per minute, was always higher in C than OM: 140.7 +/- 2.8 VS. 121.2 +/- 2.4 (P less than 0.001) with glutamate-malate and 181.1 +/- 6.3 vs. 129.7 +/- 5.2 (P less than 0.001) with succinate. A dose-response curve was constructed for each of the following: sodium ethacrynate, furosemide, chlorothiazide, acetazolamide and chlormerodrin. All diuretics inhibited C and OM equally. The 50% inhibitory molar concentration for EA was 6.2 times 10(-4); for furosemide 1.5 times 10(-3); for chlorothiazide 8.1 times 10(-3); for acetazolamide 10.8 times 10(-3); and for chlomerodrin 3.1 times 10(-5). Neither cysteine nor dithiothreitol inhibited the effect of EA. The effect of chlormerodrin was abolished by cysteine. These results demonstrate that while a difference exists between C and OM mitochondria during control studies, each of the diuretics examined exerted an equal inhibitory effect on mitochondrial respiration from both C and OM. Mercurials are the most potent inhibitors and presumably exert their effect by reacting with sulfhydryl groups. They are followed in potency by ethacrynic acid, furosemide, chlorothiazide and acetazolamide.