| Abstract: | Localization of peroxidatic catalase in human peripheral blood leukocytes was accomplished by the assessment of alkaline diaminobenzidine reaction in the cytoplasmic granules of normal and acatalasemic leukocytes. A modified cytochemical procedure of Novikoff and Goldfischer (Novikoff AB, Goldfischer S: J Histochem Cytochem 17:675, 1969) and of Fahimi (Fahimi HD:J Cell Biol 43:275, 1969) was employed to improve the specificity of alkaline diaminobenzidine test for catalase. Diaminobenzidine-positive reaction for peroxidative catalase was observed in large and medium-sized granules in the cytoplasm of normal neutrophils, but a striking and notable absence of this reaction was observed in acatalasemic neutrophils. The test for myeloperoxidase, with the diaminobenzide reaction performed at neutrality, disclosed positively stained granules in both normal and acatalasemic neutrophils. Similarities in size and configuration of the positively stained granules for these enzymes suggest that catalase is sequestered in organelles which may be primary or azurophilic granules. Myeloperoxidase has been shown to be localized in the primary granules by others. It is possible that catalase and myeloperoxidase may be sequestered together or separately in these granules, but the present data do not permit us to draw this distinction. The ultrastructural localization of peroxidatic catalase and myeloperoxidase has been attempted in eosinophils, lymphocytes, and platelets, and the observations are compared with those of neutrophilic granules. The localization of peroxidatic catalase in monocytes could not be assessed satisfactorily because of the difficulties encountered in proper sampling of these cells. |
