Effect of a choline inhibitor (N-isopropylethanolamine) on cellular metabolism of L-M cells.

N-Isopropylethanolamine, a choline analog, is incorporated into L-M cell lipids as 1,2-diacyl-sn-glycero-3-phosphoisopropylethanolamine de novo and not by base exchange. In addition, the N-isopropylethanolamine effectively blocks choline uptake, which is a reversible process. The following specific time-dependent changes in cell metabolism also occur when N-isopropylethanolamine is present: (1) a decrease in total content of phosphatidylcholine, (2) inhibition of both the cellular uptake of [3H]choline and its incorporation into phosphatidycholine, (3) a decrease in the incorporation of [3H]thymidine into DNA as early as 2 h after initiating the N-isopropylethanolamine block, (4) inhibition of the cellular uptake of [3H]uridine and incorporation into RNA 16--24 h after addition of the N-isopropylethanolamine, and (5) stimulation of the cellular uptake of [3H]leucine and an inhibition of its incorporation into protein, which reached a maximum (68% of controls) 8 h after N-isopropylethanolamine treatment.