Effect of L-methionine on contractile response, calcium influx and calcium channel blocking agents in the rat aorta.

L-Methionine incubated with aorta strips and S-adenosyl-L-methionine incubated with aorta membranes methylate membrane phospholipids. L-Methionine enhances the contractile response of helical strips of rat aorta to KCl. L-Methionine also enhances the slow component of the contractile response of rat aorta to norepinephrine associated with influx of exogenous calcium. L-Homocysteinethiolactone inhibits methylation of membrane phospholipids and depresses the contractile response to KCl and to norepinephrine. L-Methionine enhances and L-homocysteinethiolactone depresses KCl-stimulated influx of calcium into rat aorta strips. L-Methionine has no effect on calcium efflux. Tested against calcium channel blocking agents, L-methionine reduces the inhibition caused by diltiazem and chlorpromazine but not that caused by TMB 8 or verapamil. It is postulated that methylated intermediates of phospholipid methylation enhance the function of membrane calcium channels.