The controversial M cell

The Controversial M Cell. A recent publication by us has been interpreted b y some as arguing against the existence and importance of M cells. We suppo se this is the reason we have been asked to write this "controversy." Regre ttably for the controversy, neither our work nor we deny the existence of M cells. Rather, we have confirmed, conceivably ad nauseum, that M cells do exist and contribute importantly to the expression of electrical activity i n the intact myocardium. What controversy there is relates to (1) whether t here is an inhomogeneous transmural gradient for ventricular repolarization in normal hearts, and (2) why the electrophysiologic properties of differe nt myocardial sites differ so markedly at the level of the isolated tissue and single cell and yet become so much more homogenous in the intact ventri cle, These issues are addressed on the following pages.