Isolated heart myocytes: ultrastructural case study technique

We have developed a method for performing case studies of heart muscle cells enzymatically isolated from the ventricular walls of rats that is a simple and inexpensive adaptation of procedures developed for the examination of monolayers of attached, cultured cells. The technique represents a marked departure from published accounts of electron microscopic studies of pellets or monolayers from a population of potentially heterogeneous isolated myocytes. Here we report the method, which we have used under controlled conditions with 0 mmol and 1 mmol added CaCl2, to correlate sarcomere length and electrical stimulatibility in the living state with ultrastructural features that include the relative disposition of myofilaments and the integrity of the cell coat. The degree of shrinkage during the preparative steps in less than 5%, as directly determined from photographs of striations in the living, fixed, and embedded states.