Abstract
The interactions between auto-oxidized 3,3'-diaminobenzidine (DAB oxide) and mitochondria and peroxisomes were studied electron microscopically. Mitochondria were visualized in heart and liver thoroughly fixed with glutaraldehyde or formaldehyde after incubation in auto-oxidized DAB medium. Dense deposits were seen along the inner membranes of the mitochondria probably due to coupling of DAB oxide with cytochrome c and possibly with cytochrome a, but not with b type cytochromes. This reaction in formol-fixed tissues was stable to heat for 20 min at 80°C. Dense deposits of conjugated catalase of hepatic peroxisomes occurred in the matrices, and the reaction was sensitive to 3-amino-1,2,4-triazole. Heating for 30 min at 120°C of formol-fixed liver had no effect on this reaction while enzyme activities of peroxisome catalase were destroyed. With incubation in fresh DAB medium for 3 hr no staining of cytoplasmic organelles was visualized. These reactions of DAB oxide were nonenzymatic and resulted from physical bindings. The possible chemical states of DAB oxide are discussed. Some free radicals were detected in the precipitates, but no information has been obtained from aqueous solutions. The auto-oxidation of DAB is mainly a photo-oxidation.