Cell-type differences in the serum and cyclic AMP-dependent regulation of ornithine decarboxylase activity in two cultured fibroblast types.

Serum re-feeding stimulated ornithine decarboxylase (ODC) activity 8 to 10-fold in FS fibroblasts and 5 to 8-fold in 3T3 fibroblasts. Addition of dibutyryl cyclic AMP or 3-isobutyl-1-methylxanthine at the time of serum re-feeding further stimulated ODC activity in 3T3 fibroblasts but inhibited the serum stimulation of ODC activity in FS fibroblasts. It is suggested that serum and cyclic AMP independently regulate ODC activity in cultured fibroblasts.