Comparison of protein constituents between atria and ventricles from various vertebrates by two-dimensional gel electrophoresis.

1. Protein constituents of cardiac muscles of 23 species were examined by two-dimensional gel electrophoresis in order to find the difference in protein components between atria and ventricles. 2. Protein compositions of atria were similar to those of ventricles, however, differences were found in myosin and some other proteins in most species. 3. A major protein with molecular weights of 12,000-15,000 daltons was distributed only in atria from mammals. 4. The atrioventricular difference suggested that the ventricular tissue was more specialized in mammals than in birds, as compared with the atrial tissue.