Human neuroblastoma cholinergic LA-N-2 cells were used as an experimental model to test the possibility that the methylation of phosphoethanolamine (PEtn) to phosphocholine (PCho) and free choline (Cho) (Andriamampandry et al. 1989) could contribute to acetylcholine (AcCho) synthesis. LA-N-2 cells were incubated with 3HCho for 90 min and 22.7 of 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 10μM 3Hethanolamine (Etn) into MeEtn, PMeEtn, PMe2Etn and their corresponding phospholipids was reduced in cells incubated in medium containing 7.2μM choline as compared to cells incubated in medium devoid of choline indicating that the lack of Cho from the incubation medium stimulated the conversion of PEtn to Cho water soluble derivatives. Incubation of LA-N-2 cells with 3HEtn led to the labelling of 3HAcCho. Cultures incubated in parallel with 3HCho showed that roughly 10 of 3HAcCho obtained after 16 hrs of incubation with the Cho label derived from 3HEtn. The synthesis of Cho and AcCho from Etn may be enhanced after cellular differentiation induced by the growth of the cells in the presence of retinoic acid (RA). The results indicate that the methylation of 3HEtn and/or of 3HPEtn may be used by cholinergic neurons as precursor for AcCh
展开▼
