Myeloid cells are known to contain myeloperoxidase (MPO) and catalase. This study has used MPO and catalase replete and deficient myeloid cell lines to clarify the localization of these components using 3,3’-diaminobenzidine (DAB) ultrastructural cytochemistry. Conditions of DAB incubation can be modified to preferentially stain catalase (alkaline at pH 9.7) or MPO (neutral at pH 7.0-7.6), but crossreactivity persists, preventing the discrimination between catalase and peroxidase. Biochemical assays demonstrated both MPO and catalase in HL60 cells; similar amounts of catalase but no MPO activity in the A7 cell line; increased amounts of catalase but no MPO activity in the HP50 and HP100 cell lines; and neither MPO nor catalase in the KG1 cell line. Neutral DAB stained MPO (pH 7.4; [DAB] 5 or 20 mg/10 mL 0.05 M Tris; 30 min or 120 min; 24° or 37°C; 0.01% H2O2) in HL60 (Fig. 1), but not in A7. Alkaline DAB intensely stained catalase (pH 9.7; 20 mg/10 mL; 120 min; 37°C; 0.01% or 0.03%) in A7.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.