Influence of age, sex and cancer on the activities of gamma-glutamyl transpeptidase and of dipeptidyl aminopeptidase IV in rat tissues.

gamma-Glutamyl transpeptidase (GTP; EC 2.3.2.2) is an enzyme known to show activity changes during development and carcinogenesis. Its activity was measured in the livers and lungs of female and male rats of different ages, in Morris hepatomas and in experimentally induced pancreatic carcinomas. For comparison purposes, the activity of another peptidase, dipeptidyl aminopeptidase IV (DPAP; EC 3.4.14.1), was assayed in the same tissues. GTP activity was high in fetal liver and hepatomas, but low in adult rat liver, with a marked sex difference, 3 times higher in the female than in the male. In the pancreas, however, the activity of the enzyme was high in the adult but low in the fetus and in pancreatic carcinoma. There were no marked developmental changes or sex differences in pulmonary GTP activities. DPAP levels were low in fetal and neonatal liver and lung, they increased rapidly after birth and showed no sex differences in the adult. In Morris hepatomas and in pancreatic tumors the activity of DPAP was significantly lower than in normal adult liver and pancreas. These results suggest that measurements of GTP (and, to a lesser extent, DPAP) are remarkably suitable for the study of neoplastic cells and tissues.