The modulation of the induction of ornithine decarboxylase by spermine, spermidine and diamines

Early changes in ornithine decarboxylase activity during Friend leukemia cell differentiation

Agents such as dimethylsulfoxide, N,N'-dimethylformamide and bisacetyldiaminopentane that induce erythroid differentiation of Friend leukemia cells, cause a rapid increase in ornithine decarboxylase (EC 4.1.1.17) activity in intact cells during the 'latent' period preceding the accumulation of hemoglobin-containing cells. Blockage of erythroid differentiation with 5-bromo-2'-deoxyuridine did not prevent these alterations in enzyme activity. Addition of each chemical inducer in the extracts of these cells stimulate the basal levels of ornithine decarboxylase activity. These data indicate that the chemical inducers of differentiation modify the normal pattern of ornithine decarboxylase activity in this system.

Inhibition of polyamine accumulation and cell proliferation by derivatives of diaminopropane in Ehrlich ascites cells grown in culture

1. 1,3-Diaminopropane and some of its derivatives are potent inhibitors of ornithine decarboxylase (EC 4.1.1.17) in Ehrlich ascites cells grown in suspension culture. Among the amine derivatives tested, 1,3-diamino-2-propanol most effectively prevented any accumulation of spermidine and spermine in ascites cells when the proliferation was stimulated by diluting the cells with fresh medium. 2. The effectiveness of diaminopropanol in abolishing polyamine accumulation was primarily based on a rapid decay of ornithine decarboxylase activity following the exposure of the cells to the drug. 3. The mechanism of action of diaminopropanol on ornithine decarboxylase apparently involved a formation of macromolecular inhibitors or 'antizymes' to the enzyme. 4. Even though the inhibitory effect of 1,3-diaminopropane on polyamine accumulation approached that of diaminopropanol, the former compound only marginally inhibited the incorporation of [3H]thymidine into DNA and that of [14C]leucine into protein, in contrast to the marked depression of macromolecular synthesis produced by diaminopropanol. The apparent dissociation of polyamine depletion brought about by 1,3-diaminopropane from an antiproliferative action was apparently due to the fact that diaminopropane, unlike diaminopropanol, was partially capable of taking over the function of natural polyamines. 5. The inhibition of DNA and protein synthesis as well as the prevention of increase in cell number by diaminopropanol was closely associated with polyamine depletion and was fully comparable, as regards timing and magnitude, with that achieved with difluoromethylornithine. The antiproliferative effect of diaminopropanol, however, was only partly reversed by a simultaneous addition of putrescine (or spermidine) into the culture medium. The lack of a complete reversal of the action of diaminopropanol on cell growth by natural polyamines was apparently due to the fact that it was remarkably difficult or even impossible to increase intracellular polyamine concentrations by exogenous polyamines in the presence of diaminopropanol. Nevertheless, the diaminopropanol-induced arrest of growth was reversible as judged by a rapid increase in ornithine decarboxylase activity followed by restoration of DNA synthesis.

Two distinct mechanisms for ornithine decarboxylase regulation by polyamines in rat hepatoma cells

Exogenous diamines and polyamines added to rat hepatoma (HTC) cells in culture rapidly decrease ornithine decarboxylase (ODC) activity. Previous evidence has suggested that these amines set either at the level of blocking new enzyme synthesis or by the induction of a non-competitive protein inhibitor, termed antizyme, which complexes with ODC to form an inactive complex. Wth the use of HMOA cells, a recently cloned rat hepatoma cell line that has a greatly stabilized ODC, it has been possible to demonstrate that 10(-5) M of exogenous putrescine blocks the increase in ODC activity, but unlike in the parent HTC cell line, without induction of the antizyme or formation of any inactive ODC-antizyme complex. However, complete blockade of ODC at 10(-2) M putrescine is effected by induction of antizyme and formation of the ODC-antizyme complex, as now evidenced by the isolation of the active enzyme and antizyme components after Sephadex column chromatography in the presence of 250 mM NaCl. These findings indicate clearly that two polyamine-regulatory mechanisms for ODC exist and are separable in this cell line.