SURFACE ULTRASTRUCTURAL FEATURES OF ISOLATED PERFUSED RAT HEARTS DURING CALCIUM PARADOX

  • 1 January 1981
    • journal article
    • research article
    • p. 109-114
Abstract
Cellular damage caused by Ca2+ paradox is of significant importance under both experimental and clinical conditions. EM was used to study the surface changes of isolated Sprague-Dawley rat hearts perfused with normal Krebs-Henseleit (KH) medium, Ca2+-free KH medium, Ca2+-free KH medium followed by normal KH medium. The hearts perfused with Ca2+-free medium and normal KH medium showed elongated parallel myofibrils with transverse ridges spaced at regular intervals. The major change in Ca2+-free hearts consisted of wide cellular separation. For the Ca2+-paradox hearts, the myofibrils were twisted and narrowed at several locations. The myocardial fiber surfaces were bulged out, frequently with sarcolemmal ruptures and holes. Supercontraction of cells caused breaks in the sarcolemma and aggregation of mitochondria at the cell periphery. Ca2+-depletion apparently primarily affects the myocardial cell junctions which, following reintroduction of Ca2+, accelerate the entry of Ca2+ into the cells, supercontraction of cells and stretching of sarcolemma.