EFFECTS OF ETHACRYNIC-ACID AND FUROSEMIDE ON ISOLATED RAT-KIDNEY MITOCHONDRIA - INHIBITION OF ELECTRON-TRANSPORT IN REGION OF PHOSPHORYLATION SITE 2

Abstract

Ethacrynic acid and furosemide inhibit the respiration of isolated mitochondria which suggested a direct action of these diuretics on oxidative metabolism. The effects of ethacrynic acid and furosemide on the O2 consumption of mitochondria isolated from the cortex and outer medulla of rat kidneys were investigated. Both diuretics inhibited state 3 and uncoupled respiration supported by glutamate-malate (which enters the electron transport chain prior to site I) and succinate (which enters prior to site II); respiration supported by tetramethyl phenylene diamine-ascorbate (which enters prior to site III) was relatively unaffected. Biochemical bypass of site II significantly alleviated the respiratory inhibition of both agents. The electron transport carriers were measured by dual wavelength spectroscopy, which showed that both diuretics caused a reduction of flavoproteins and an oxidation of the cytochromes. Ethacrynic acid and furosemide inhibit oxidative phosphorylation in vitro by inhibiting electron transport through phosphorylation site II.