DIFFERENT DISTRIBUTIONS OF MICROTUBULES, DESMIN FILAMENTS AND ISOMYOSINS DURING THE ONSET OF CARDIAC-HYPERTROPHY IN THE RAT

  • 1 January 1984
    • journal article
    • research article
    • Vol. 34  (2) , 300-306
Abstract
To elucidate the role of the cytoskeleton in the development of adult heart, microtubules and intermediate filaments of desmin were studied in young and adult rat heart myocytes during the onset of growth, after mechanical overloading induced by aortic stenosis. Such overloading is known to cause heart hypertrophy by stimulating overall protein synthesis, and to initiate a shift in myosin isozymes. For this study, double immunolabeling of isolated myocytes was used with sepcific antibodies raised against tubulin, desmin and the 2 main isomyosins V1 and V3. Whereas desmin remained unchanged, tubulin was redistributed in arrays parallel to the long axis of the myocytes, and was densest around the nuclei. Alterations in the microtubule pattern were observed very early after aortic stenosis, during the onset of heart growth; they were transitory, and did not occur simultaneously in all myocytes. Chronological examination of myocytes labeling with both antitubulin and anti V3 myosin clearly suggested that the transitory alteration in the microtubule pattern was an early event preceding the change in the expression of the myosin gene. Results, observed in young rats, in which mitosis is stimulated by overloading, and in adult rats, exhibiting no mitosis, showed that microtubules are involved in the development of cells in which mitosis does not occur. This is the first evidence of a correlation in functional adult heart, between the reorganization of cytoplasmic microtubules and the onset of growth.