Biochemical evidence for cellular dedifferentiation in adult rat cardiac muscle cells in culture: expression of myosin isozymes.

Myosin isozyme pattern in adult rat cardiac ventricular muscle cells in long-term culture was investigated. The myosin isozymes profile of cultured cardiac myocytes underwent a change in a serum-containing medium from two weeks onward, showing an embryonic rat ventricular myosin isozymes pattern that contained predominant isozyme V3. When adult cardiac myocytes were grown in a serum-containing medium supplemented with T4, these cells contained a predominant V1 band whose electrophoretic mobility and Ca2+-ATPase activity were comparable to those of the adult rat ventricle in vivo. This study has demonstrated that the adult cardiac ventricular muscle cells in long-term culture contain a predominant myosin isozyme V3 unlike their counterparts in vivo. Supplemented T4 modulated the embryonic type isozyme V3 to the adult type V1.