LIGHT-MICROSCOPIC CATALASE HISTOCHEMISTRY IN MUSSEL DIGESTIVE GLAND TISSUE

Different light microscopical procedures for the histochemical demonst ration of catalase were tested in cryostat sections of mussel digestiv e gland tissue by using both benzidine and diaminobenzidine (DAB) as h ydrogen donors. The selected procedure, which was also applied to mous e liver for comparative purposes, consisted of incubation in media con taining 0.2% DAB and 0.3% H2O2 at pH 10.4 for 35 min at 42-degrees-C. Addition of 0.01 M imidazole to the incubation medium increased the st aining intensity of the histochemical procedure. The positive reaction product was localized in epithelial cells lining the digestive tubule s and the ducts. The histochemical reaction was inhibited partially by aminotriazole or sodium azide and disappeared completely by omission of H2O2 from the incubation medium. On the other hand, heat resistant non-enzymatic reactions were observed in sites known to contain lipofu scins such as epithelial cells of the gastrointestinal tract and conne ctive tissue brown cells.