INDUCTION OF GAMMA-GLUTAMYL-TRANSFERASE TRANSPEPTIDASE ACTIVITY BY DIETARY PHENOBARBITAL IN SPONTANEOUS HEPATIC-TUMORS OF C3H MICE

  • 1 January 1980
    • journal article
    • research article
    • Vol. 71  (4) , 536-542
Abstract
Biochemical features of spontaneous hepatic tumors in C3H mice were studied histochemically in comparison with those of neoplastic lesions developed in animals fed dietary phenobarbital (PB) continuously or treated with diethylnitrosamine (DEN) during 11-14 wk of age. All 42 spontaneous hepatic tumors that developed in control mice by 74 wk of age were completely negative for .gamma.-glutamyl transpeptidase (.gamma.-GTPase) activity. Dietary phenobarbital enhanced hepatic tumorigenesis remarkably, and 32 of 43 tumors found at 70 wk showed multifocal .gamma.-GTPase activity. DEN induced .gamma.-GTPase-positive islands of hepatocytes, but 12 of 13 tumors > 5 mm in diameter that developed by 60 wk were .gamma.-GTPase-negative. The phenomenon of induction of .gamma.-GTPase activity by PB in spontaneous hepatic tumors appears important for elucidating the mechanism of promotion by PB and also for analyzing multisteps of carcinogenesis.