Fine structural localization of glucose-6-phosphatase activity in the pancreatic islets of two amphibian species (Salamandra salamandra L. and Rana esculenta L.).

The ultrastructural distribution of glucose-6-phosphatase activity has been investigated in the salamander and frog pancreas. In the pancreas of salamander the enzyme was located in the A-cells, while in frog it occurred in all main types of islet cells B-, A-, and D-cells). As a rule, the reaction intensity was higher in the frog islet cells. No reaction was recorded in the exocrine pancreatic tissue of both species. The glucose-6-phosphatase activity was constantly detected in the lumen of rough endoplasmic reticulum and between the nuclear envelopes. Other enzyme localizations, observed especially in the A-cells of the salamander pancreas, were considered possible diffusion artifacts ro remnants of other phosphatase activity. The enzyme distribution in different types of islet cells, as well as its functional significance are discussed in relation to the findings of other authors.