MYOSIN POLYMORPHISM IN FISH CARDIAC MUSCLES

1. Native myosin and myosin heavy chain of ventricular and atrial musc les of some teleost species were analysed electrophoretically. 2. The presence of single isoforms of native myosin and myosin heavy chain in the whole ventricle of carp, tench, pike and rainbow trout suggests t hat both layers of ventricular myocardium (compact and spongious) expr ess similar, or even the same, myosin. 3. Ventricle and atrium contain distinct isoforms of native myosin and/or myosin heavy chain. It is s uggested that differences in MHC content in ventricular and atrial myo cardium may imply different contractile properties of these muscles.