CALCIUM-RELATED CHANGES IN THE ULTRASTRUCTURE OF MAMMALIAN MYOCARDIUM

  • 1 January 1979
    • journal article
    • research article
    • Vol. 60  (1) , 96-106
Abstract
Isolated rat hearts, perfused with Ca2+-free medium for 5 min, were perfusion-fixed for ultrastructural studies. Increased pinocytotic activity and characteristic changes in the staining of the intercalated disc, coupled with conspicuous staining of the middle lamina in the tight junctions in the hearts, indicated a change in the sarcolemmal activity and cell-cell relationship. The intracellular effects of Ca2+-free perfusion were indicated by the presence of an active Golgi body and the loss of heterogenic staining of the nucleoplasm. The latter appears to be a direct consequence of Ca2+ depletion of the cell, as heterogeneity reappeared upon reintroduction of the Ca in the perfusion medium. The extent of structural damage upon reintroduction of Ca was dependent upon the extracellular Ca concentration. Apparently perfusion with Ca2+-free medium causes some membrane changes in the heart which probably make it more vulnerable to the reintroduction of Ca. The structural damage seen on Ca reintroduction appeared to be related to the amount of Ca overload.