Quantitative histochemical methods have been used for the assay of 6-phosphogluconic dehydrogenase (6-PGDH), isocitric dehydrogenase (ICDH), peptidase (PEPT), and adenosine triphosphatase (ATPase) in the microdissected islets and acinar tissue obtained from normal and alloxan diabetic rats.

6-PGDH activity of the islets following alloxanization showed an increase at twelve hours; maximal change was observed at seventy-two hours. There was no consistent and significant increase in the enzyme activity of the acinar tissue following alloxanization.

ICDH activity of rat islet was increased significantly at twelve hours but decreased at twenty-four hours after alloxanization. At forty-eight and seventy-two hours the enzyme activity of the islet returned to normal. Enzyme activity of the acinar tissue showed no particular trend, although at twenty-four hours following alloxanization it was significantly lower than in the controls.

Changes in islet peptidase activity were more marked. Following alloxanization the islet enzyme activity decreased significantly up to twenty-four hours; at forty-eight hours it showed marked increase and was between two- and threefold that of the value at twenty-four hours. It should be noted that this increase in the islet peptidase activity coincides with the period of disappearance of the beta cells.

No immediate effect of alloxan injection was noted on the ATPase activity of the rat islet tissues during the first two hours. This is contrary to the reports of some earlierworkers.

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