INTERACTION OF TAURINE WITH METHIONINE - INHIBITION OF MYOCARDIAL PHOSPHOLIPID METHYLTRANSFERASE

Perfusion of isolated, working rat heart with buffer containing 300-mu-M methionine in the presence of 2.5 U/L insulin led to a 15% decrease in cardiac work and a four-fold decrease in sarcolemmal Na+-Ca2+ exchange activity. These effects of methionine were largely prevented by inclusion of 10 mM taurine in the buffer supplemented with methionine and insulin. Taurine also reduced the extent of H-3-methyl group incorporation from radioactive methionine into myocardial phospholipids by approximately 45%. Assays of sarcolemmal phospholipid methyltransferase activity at catalytic sites I, II, and III revealed that taurine inhibited N-methylation activity approximately 30%. The data imply that the ability of taurine to modulate myocardial contraction and calcium transport may be related to taurine-mediated inhibition of phospholipid N-methylation.