Myofibrillar organization and desmin in rat heart myocytes

The distribution of desmin, and alpha-actinin was studied in vivo growing rat heart myocytes and in vitro cultured heart myocytes using double indirect immunofluorescence labelling. Myocytes growing in vivo exhibited a superimposable pattern of alpha-actinin and desmin at the level of the Z discs and intercalated discs. Cultured neonate rat heart myocytes concurrently exhibited changes in shape and a loss of myofibrillar register. Whereas alpha-actinin staining remained unchanged, that of desmin disappeared from the Z discs but persisted as cables and randomly oriented foci throughout the sarcoplasm. We conclude that desmin binding to the Z discs is correlated with the in register organization of myofibrils.