title: Calcium dependence for increased antizyme inhibitory activity of ornithine decarboxylase in rat glioma cells.
abstract: Ornithine decarboxylase activity was inhibited by the antizyme inhibitor protein in extracts from C6-2B rat glioma cells. Antizyme activity in C6-2B cells was increased 3- to 10-fold by micromolar concentrations of putrescine, spermidine and spermine. The calcium chelator EGTA (pCa 6.4) inhibited basal and polyamine-stimulated antizyme activity, and this inhibition was prevented by concurrent incubation with calcium, but not with magnesium. EGTA appeared to block antizyme synthesis, because the half-life values of antizyme activity in the presence of EGTA or cycloheximide were similar (121-143 min). Also, calcium readdition rapidly reversed EGTA inhibition of antizyme activity by a mechanism which could be blocked by cycloheximide. The ability of EGTA to inhibit spermidine-stimulated antizyme activity was not due to reduced spermidine uptake, because EGTA actually stimulated [3H]spermidine accumulation in the trichloroacetic acid-soluble fraction of C6-2B cells after 3 h.
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D005910:Glioma / Q000201:enzymology*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D065108:Ornithine Decarboxylase Inhibitors; D011506:Proteins / Q000502:physiology*; D011700:Putrescine / Q000494:pharmacology; D051381:Rats; D013095:Spermidine / Q000378:metabolism / Q000494:pharmacology
chemical_list: D065108:Ornithine Decarboxylase Inhibitors; D011506:Proteins; C031017:ornithine decarboxylase antizyme; D004533:Egtazic Acid; D003513:Cycloheximide; D008274:Magnesium; D002118:Calcium; D013095:Spermidine; D011700:Putrescine