Scanning electron microscopic studies on cultured heart cells after the induction of arrhythmias and fibrillation.

Scanning electron microscopic observations were made of mouse embryonic heart cells in culture to clarify the interrelationship between morphological damage and cardiac arrhythmias and fibrillation induced by changes of ion concentrations. They were studied with particular reference to the abnormalities in the heart cell and the intercellular connections. The cells exhibited arrhythmias with any alteration in ion concentration (MgSO4, CaCl2, KCl, NaCl) in the culture medium, and they developed fibrillation-like beating under certain conditions of lowered potassium, or sodium, and increased sodium with a reduction in calcium or potassium. The heart cells showing arrhythmias were revealed by scanning electron microscopy to have more or less fine morphological changes in their slender processes, and detached or raised cell edges. Fold-like undulations in the cell body and cell ledge were also numerous in cells exhibiting fibrillation-like beating. These cell body changes may, however, be characteristic of cells maintained in cultures with lowered potassium content, since only these cultures showed such changes. Changes of cell ledge were also demonstrable in cultures with altered MgSO4, CaCl2 content or increased KCl or NaCl content although the cells in these cultures did not develop fibrillation. It was noted that there was a tendency for the changes of cell body and cell edge to be conspicuous in cells exhibiting fibrillation. The results obtained indicated that fibrillation developed only in the presence of altered concentrations of certain ions, in association with subtle morphological changes in the cells and intercellular connections.