INCORPORATION OF [H-3] ETHANOLAMINE INTO ACETYLCHOLINE BY A HUMAN CHOLINERGIC NEUROBLASTOMA CLONE

Human neuroblastoma cholinergic LA-N-2 cells were used as an experimen tal model to test the possibility that the methylation of phosphoethan olamine (PEtn) to phosphocholine (PCho) and free choline (Cho) (Andria mampandry et al. 1989) could contribute to acetylcholine (AcCho) synth esis. LA-N-2 cells were incubated with [H-3]Cho for 90 min and 22.7% o f the radioactivity was present in PCho, 18.5% in free Cho and 4.8% as AcCho. The ratio of Cho/AcCho, however, was of about 1 after 16 hours of incubation. The incorporation of 10 muM [H-3]ethanolamine (Etn) in to MeEtn, PMeEtn, PMe2Etn and their corresponding phospholipids was re duced in cells incubated in medium containing 7.2 muM choline as compa red to cells incubated in medium devoid of choline indicating that the lack of Cho from the incubation medium stimulated the conversion of P Etn to Cho water soluble derivatives. Incubation of LA-N-2 cells with [H-3]Etn led to the labelling of [H-3]AcCho. Cultures incubated in par allel with [H-3]Cho showed that roughly 10% of [H-3]AcCho obtained aft er 16 hrs of incubation with the Cho label derived from [H-3]Etn. The synthesis of Cho and AcCho from Etn may be enhanced after cellular dif ferentiation induced by the growth of the cells in the presence of ret inoic acid (RA). The results indicate that the methylation of [H-3]Etn and/or of [H-3]PEtn may be used by cholinergic neurons as precursor f or AcCho.