Normal guinea pig peritoneal cells were examined for peroxidase activity by the diaminobenzidine ultrastructural histochemical technique before and after exposure to horseradish peroxidase in vitro. Macrophages exhibited endogenous peroxidase activity in the nuclear envelope, endoplasmic reticulum, occasional golgi vesicles and saccules, and rare granules. The majority of granules and phagolysosomes from normal and horse serum-stimulated macrophages were peroxidase negative. When cells were incubated in vitro with exogenous horseradish peroxidase, the latter was localized in vesicles and vacuoles; the proportion of macrophages showing the distribution pattern of endogenous activity did not increase. The evidence thus suggests that when exogenous peroxidase is used as antigen, enzymatic activity in the endoplasmic reticulum and nuclear envelope may be attributed to endogenous enzyme. The possible nature and function of endogenous peroxidase-like activity in the peritoneal cells are discussed.
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Cotran et al. (1970) studied this question.