The effect of lithium, imipramine and chlorpromazine on the membrane bound enzyme phosphatidylethanolamine methyltransferase.

The activity of phosphatidylethanolamine methyltransferase (PMT) in disrupted human erythrocytes and ghost cells was inhibited by lithium (Li+), imipramine and chlorpromazine. There was no inhibitory effect of the drugs in concentrations similar to the average therapeutic blood levels. Li+ exerted an inhibition on PMT activity in hemolysates at concentrations 8 times the average therapeutic level whereas chlorpromazine and imipramine showed an inhibitory effect on PMT in hemolysates at 10(3) fold their respective therapeutic serum level.