Ultrastructure of the sarcolemma and intercalated disc in isolated rat myocytes

The ultrastructure of the sarcolemma in isolated calcium-tolerant myocytes has been compared with that of myocytes in the intact heart, using thin section and freeze-fracture electron microscopical techniques. Data on the density and distribution of intramembrane particles and on the topography of Z-folds in the general (i.e. non-disc) sarcolemma are summarised. The fate of gap junctions on separation of the intercalated disc membranes has been studied i) at intervals after isolation, ii) using cationized ferritin as an extracellular marker and iii) by serial sectioning. The results of these studies help explain how ionic integrity of the individual isolated cells may be maintained.