ELECTROPHORETIC EVIDENCE FOR THE IMPAIRMENT OF COMPLEXES OF THE RESPIRATORY-CHAIN DURING IRON ASCORBATE INDUCED PEROXIDATION IN ISOLATED RAT-LIVER MITOCHONDRIA

The impairment of the complexes of the respiratory chain was studied in isolated rat liver mitochondria under the conditions of an iron/ascorbate-mediated oxidative stress. Using blue native electrophoresis technique the NADH-ubiquinone oxidoreductase, ubiquinol-cytochrome-c oxidoreductase, cytochrome oxidase and ATP-synthetase were separated from mitochondrial samples at different stages of peroxidation and quantified by densitometry. In the second dimension the protein complexes were separated into their individual subunits by Tricine/SDS-electrophoresis. In relation to the time course of lipid peroxidation protein losses were moderate in the exponential phase and enhanced towards plateau phase of TEARS formation, when the intensity of staining for the native complexes became reduced by 84%, 69%, 63% and 24% for complexes I, III, V and IV, respectively, and a high molecular aggregation band as a putative marker of oxidative stress was formed. The decline of overall staining by 23%, a decrease in trichloroacetic acid precipitable protein and the formation of acid soluble primary amines suggest the occurrence of fragmentation or degradation processes. Apparently, the impairment of the respiratory chain complexes during peroxidation was not reflected in altered electrophoretic mobilities or specific losses of protein subunits of these innermitochondrial membrane components.