Early changes in ornithine decarboxylase activity and polyamines during erythroid differentiation of Friend leukemia cells.

Induction of cytosolic L-ornithine decarboxylase (ODC) activity in cultures of Friend erythroleukemia cells by seeding in fresh medium was suppressed by treatment with several differentiation inducers. The levels of suppression after 3 h treatment were about 60% at 20 mM nicotinamide, 30% at 1.5% dimethyl sulfoxide (DMSO), and 20% at 5 mM hexamethylene bisacetamide (HMBA). Tracer experiments using [3H]ornithine to determine newly accumulated polyamines including putrescine revealed that the accumulation was suppressed by treatment (18 h) with the inducers. Furthermore, results of polyamine determination by high-pressure liquid chromatography showed that the cellular polyamine content in differentiation-induced cells was lower than those of uninduced cells in early (18 h after inducer treatment) stages of differentiation. Accordingly, it is suggested that cytosolic ODC levels virtually represent the rate of accumulation of intracellular polyamines in the early period of differentiation.