HISTOCHEMICAL-LOCALIZATION OF GAMMA-GLUTAMYL-TRANSPEPTIDASE IN MIDGUTTISSUES OF MARINE MUSSELS

The light microscopical localization of gamma-glutamyl transpeptidase (GGT) was studied in midgut tissues of the mussel Mytilus galloprovinc ialis Lmk (Mollusca, Bivalvia). The apical portion of the stomach epit helial cells showed an intense positive red coloration, particularly i ntense in the gastric shield region of the stomach, while the differen t portions of the intestine were negative. The red granular reaction p roduct was also deposited in non-ciliated cells lining the collecting ducts and in cells lining some digestive tubules. In the latter, the r eaction product showed a patchy distribution pattern and was apparentl y localized within basophilic cells. These results are discussed in co nnection with the involvement of GGT activity in various important met abolic pathways, specially in the process of extracellular digestion i n bivalve molluscs.