Effects of Ca2+ ionophore A23187, 1,2-dioctanoylglycerol, and dibutyryl cAMP on the activity and expression of ornithine decarboxylase in guinea pig lymphocytes.

The Ca2+ ionophore A23187 induced small increases in ornithine decarboxylase activity and ornithine decarboxylase mRNA in guinea pig lymphocytes. 1,2-Dioctanoylglycerol potentiated the A23187-induced ornithine decarboxylase activity and the accumulation of mRNA for this enzyme. Dibutyryl cAMP also potentiated the enzyme activity, but had little effect on the accumulation of mRNA. 1,2-Dioctanoylglycerol and 12-O-tetradecanoylphorbol-13-acetate potentiated ornithine decarboxylase activity that had been increased by treatment with both A23187 and dibutyryl cAMP with a consistent increase in the ornithine decarboxylase mRNA. However, dibutyryl cAMP augmented ornithine decarboxylase activity that had been increased by the combination of A23187 and 1,2-dioctanoylglycerol without affecting the ornithine decarboxylase mRNA level. These results suggest that the protein kinase C and cyclic AMP pathways are involved in the enhancement of ornithine decarboxylase activity in guinea pig lymphocytes, but that the mechanisms of the enhancement differ for each pathway, the former increasing the ornithine decarboxylase mRNA level, but not the latter.