γ-Glutamyl Transpeptidase in Transplantable, Chemically Induced Rat Hepatomas and “Spontaneous” Mouse Hepatomas<xref ref-type="fn" rid="FN2">2</xref>

Abstract

In our previous work, we found high levels of a polarographically active thiol compound in several transplantable hepatomas of chemical origin. High levels of this compound were found also in extracts from primary hepatomas induced by 3′-methyl-4-dimethylaminoazo-benzene. In the present work this compound was identified as L-cysteine. Cysteine was formed from glutathione by a high level of the enzyme γ-glutamyl transpeptidase (glutathionase). The level of glutathionase in fetal and normal neonatal rat liver was as high as in rat hepatomas, but in adult rat liver the activity of this enzyme was only 1/50–1/100 that in hepatomas. In mice, as in rats, the neonatal liver contained a high, the adult liver a low, level of glutathionase, but among 4 mouse hepatomas of “spontaneous” origin, 3 showed no change. The high activity of glutathionase appears to be a distinctive feature of at least some chemically induced rat hepatomas.