Ornithine decarboxylase lability in 2 transplantable highly deviated rat hepatomas.

Abstract A strong ornithine decarboxylase (ODC)-inactivating capacity has been previously shown (M.F. Zuretti and E. Gravela (1983) Biochim. Biophys. Acta, 742, 269–277) to be bound to rat liver microsomes. Present results show that in 2 fast-growing transplantable tumors, the 3924A Morris hepatoma and the AH 130 Yoshida ascites hepatoma, microsomes are endowed with a greatly enhanced ODC-inactivating capacity, and, concurrently, ODC displays an extreme in vitro lability and an unusual thiol-dependency (most of the activity requires dithiothreitol supply to be determined). These data are at variance with those previously obtained in hepatomas induced by N -2-fluorenylacetamide (E. Gravela et al., (1983) Cancer Res., 43, 2298–2300). The possibility that ODC lability in the 2 hepatomas here studied may result from in vivo exposure to a strong microsomal activity is considered.