Rapid Publication Isozymic Changes in Myosin of Human Atrial Myocardium Induced by Overload Monoclonal Antibodies Study Using

A bstract. An immunohistochemical study using monoclonal antibodies specific for the heavy chains ofeither human atrial (HCa) or ventricular (HC(#) myosin was performed to clarify the distribution ofeach isozyme in normal as well as pressure-overloaded human hearts. In normal human ventricles, all muscle fibers were stained by a monoclonal antibody (HMC14) specific for HC(, whereas a small number of fibers reacted with a monoclonal antibody (CMA19) specific for HCa. In contrast, in normal human atria, almost all muscle fibers were stained by CMA19, and a relatively larger number of muscle fibers also reacted with HMC 14. Furthermore, in pressure-overloaded atria, muscle fibers reactive with HMC14 were strikingly increased while those reactive with CMA 19 showed a corresponding decrease. The extent ofthis isozymic redistribution was in good correlation with atrial pressure. These results not only confirmed the existence of isoforms of myosin heavy chain in human hearts, but also demonstrated that redistribution of isomyosins could occur as an adaptation to pressure overload.