REACTION SITES BY CERIUM-CYTOCHEMISTRY FOR THE HYDROGEN-PEROXIDE GENERATING ENZYMES IN THE MONGOLIAN GERBIL PAROTID GLAND

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In order to cytochemically demonstrate the endogenous glandular source of hydrogen-peroxide (H₂O₂), which is a component of the salivary peroxidase antimicrobial system, we applied the cerium method to the Mongolian gerbil parotid gland. When NADH and NADPH were used as substrates of the H₂O₂ generating enzyme, reaction products were observed in association with the plasma membrane and pinocytotic vesicles of the myoepithelial cell. No reaction product was formed in the absence of these substrates. The reaction was inhibited by the addition to the complete medium of catalase (H₂O₂ scavenger) or of p-benzoquinone (O₂^-scavenger), or by heating prior to incubation. These results suggest that NADH- and NADPH-dependent H₂O₂ generating oxidase may be present in the myoepithelial cell. In addition, electron-dense precipitates, formed by the reaction of cerous ions, were also observed on the outer surface of the luminar plasma membrane of acinar and intercalated duct cells, and in the cristae and outer compartment of mitochondria mainly of duct cells. However, these reaction products were formed whether the substrates were contained in the cerium medium or not. Since the reaction was also weakened by catalase or p-benzoquinone, or by preheating, it is likely that some endogenous H₂O₂^-generating factors, independent bf the exogenous substrates, may exist in these sites.