HISTOCHEMICAL LOCALIZATION OF GAMMA-GLUTAMYL TRANSPEPTIDASE IN MIDGUT TISSUES OF MARINE MUSSELS

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The light microscopical localization of gamma-glutamyl transpeptidase (GGT) was studied in midgut tissues of the mussel Mytilus galloprovincialis Lmk (Molluscs, Bivalvia). The apical portion of the stomach epithelial cells showed an intense positive red coloration, particularly intense in the gastric shield region of the stomach, while the different portions of the intestine were negative. The red granular reaction product was also deposited in non-ciliated cells lining the collecting ducts and in cells lining some digestive tubules. In the latter, the reaction product showed a patchy distribution pattern and was apparently localized within basophilic cells. These results are discussed in connection with the involvement of GGT activity in various important metabolic pathways, specially in the process of extracellular digestion in bivalve molluscs.