Relative in vitro stability of ornithine decarboxylase from liver preneoplastic nodules and hepatomas.

A very rapid and drastic microsome-dependent in vitro inactivation of the hydrocortisone-induced ornithine decarboxylase in rat liver was reported recently (M. F. Zuretti and E. Gravela, Biochim. Biophys. Acta, 742: 269–277, 1983). Present results show that ornithine decarboxylase from preneoplastic nodules and hepatomas, which have been induced in rats by N -2-fluorenylacetamide, is much more stable, its greater stability not being accounted for by a lower microsome-bound inactivating capacity. The possibility of a relationship between the in vitro enzyme stability and the increase of enzyme activity in neoplastic tissues is suggested.