Cholinergic differentiation of clonal rat pheochromocytoma cells (PC12) induced by retinoic acid: increase of choline acetyltransferase activity and decrease of tyrosine hydroxylase activity.

The effects of retinoic acid (RA), a naturally occurring metabolite of vitamin A, on the growth, morphology and neurochemical differentiation of the PC12 clone of rat pheochromocytoma cells were investigated. RA added to the medium inhibited the growth of PC12 cells in a dose-dependent manner up to 10 microM without affecting their morphology. In PC12 cells cultured in the presence of 10 microM RA for 8 days, the specific activity of choline acetyltransferase (ChAT) was increased 2-fold, while the specific activity of tyrosine hydroxylase (TH) was decreased 0.5-fold compared with cells cultured in the absence of RA. Specific activities of acetylcholinesterase (AChE), glutamate decarboxylase (GAD) and lactate dehydrogenase (LDH) were not affected by RA. Both the increase of ChAT and the decrease of TH induced by RA exhibited similar time and dose dependencies. RA inhibited the increase of TH activity induced by nerve growth factor (NGF), an adrenergic neuronotrophic factor on PC12 cells. From these observations it was concluded that RA induces a cholinergic neurochemical differentiation of PC12 cells independent of a morphological differentiation.