Distributions of vimentin and desmin filaments in embryonic cardiac muscle cells in culture.

Immunofluorescence studies on the distributions of vimentin and desmin in embryonic rat cardiac muscle cells in culture were carried out, using antibodies against vimentin and desmin. The cell culture was continued for 5 days. Both vimentin and desmin increased in concentration as the cardiac myocytes matured in culture. Vimentin and desmin were mainly organized as filamentous structures and oriented in longitudinal and other directions within the cytoplasm of the cells. Cross-striated fluorescence of vimentin and desmin was rarely observed in cardiac myocytes, although cross-striated myofibrils were present during early and late periods of culture. Desmin did not show preferential adherence to the Z-line of the cultured myocytes. Vimentin was observed on the nuclei of cardiac myocytes in the form of complex network and beaded structures during culture period. Both vimentin and desmin were present in fibroblastic cells in culture. Our observations suggest that vimentin and desmin in cardiac myocytes in culture probably provide a skeletal framework, which facilitates the assembly of myofibrils. Also, these intermediate filaments are probably involved in the organization of cellular organelles in the cell cytoplasm. The role of the intermediate filaments found on the nucleus and its periphery is probably to maintain the position of the nucleus in the cytoplasm of the cell, providing an adherence between the nucleus and adjacent cytoplasmic sites.