Respiratory chain linked H2O2 production in pigeon heart mitochondria

It has been known for many years that the succinate dehydrogenase of the intestinal nematode Ascaris lumbricoides reacts with molecular oxygen without participation of the cytochrome system under formation of HaOa [l-3] . Besides, P.K. Jensen reported that at least part of the antimycin insensitive respiration of beef heart ETPs might be due to HaOa formation [4]. It was assumed that NADH was the autoxidable component of the resplratory chain responsible for the H1Oa generation. P. Hinkle et al. [5] presented evidence for an ATP dependent HaOa formation on the substrate side of cytochrome b in submitochondrial particles of beef heart. But all these results require experimental corroboration because no method had been available for determining low concentrations of HzOZ in biological material directly. Recently, Chance and Oshino [6] approached this problem in the following way: preparations of rat liver mitochondria were observed with a dual wavelength spectrophotometer. Formation of compound I of peroxisomal catalase present in these preparations was considered indicative of HzOz . In the present study HZOz was determined by the horse radish peroxidase dependent reaction of HzOZ with the fluorescent dye scopoletine [7]. A decrease ‘of fluorescence intensity demonstrates directly the