ALTERATIONS IN THE METABOLISM OF CHOLINE-CONTAINING PHOSPHOLIPIDS BY LITHIUM AND CARBACHOL IN SH-SY5Y NEUROBLASTOMA-CELLS

To investigate choline phospholipid metabolism in the human neuroblast oma cell line SH-SY5Y, cultures labeled with [C-14-methyl]choline were incubated for up to 30 min in er-glucose-N-2-hydroxyethyl-piperazine- N1-2-ethane sulfonic acid (HEPES) buffer with or without 10 mmol/L LiC l. When desired, 1 mmol/L of the muscarinic agonist carbamoylcholine w as present during the last minute of incubation. When cells were expos ed for 10 min to lithium, radioactivity in phosphatidylcholine, lysoph osphatidylcholine, and sphingo-myelin was 40%-140% higher than in cont rols incubated in buffer only. This contrasted with the results from c arbamoylcholine-containing incubations, which gave radioactivities low er than or equal to controls. Carbamoylcholine added to the LiCl-conta ining incubations yielded results only minimally different from LiCl a lone. Phosphorylcholine radioactivity was also elevated by about 50% a fter 10 min incubation with LiCl with or without added carbamoylcholin e, but was wt increased in incubations with the agonist by itself. Sim ilar changes were observed for intracellular choline but after only 5 min. These data suggest that carbamoylcholine does wt stimulate phosph atidylcholine degradation, whereas LiCl can significantly affect its m etabolism and may affect signal transduction via second messengers in human neuroblastoma cells.