Effect of Cinchona bark alkaloids and chloroquine on phospholipid synthesis. K+ channel blockers specifically enhance the activity of the serine base exchange enzyme system in Jurkat T cells.

The effects of quinine, quinidine, cinchonine, cinchonidine and chloroquine on phospolipid synthesis in the Jurkat T cell line have been compared. It was found that the two potassium channel blockers, quinine and quinidine, markedly enhanced phosphatidylserine synthesis and strongly decreased both phosphatidylcholine and phosphatidylethanolamine synthesis. The inhibition of phosphatidylcholine and phosphatidylethanolamine synthesis was due to the inhibition of the uptake of [3H]choline or [3H]ethanolamine, respectively, by the cells. This effect was also observed when using either cinchonine, cinchonidine and chloroquine. In contrast, these three drugs were unable to modify phosphatidylserine synthesis, indicating that the K+ channel blockers, quinine and quinidine, specifically interfere with the synthesis of this phospholipid.