Intracellular Ca dynamics and sarcomere length in single ventricular myocytes

The measurements of the sarcomere length in dissociated cardiac ventricular myocytes are discussed using mainly our own experimental data. The striation periodicity of these unloaded cells was found to be that which is to be expected of a myocyte free of the ultrastrucural constraints imposed upon it by the normal syncytial matrix of the ventricular wall. The sarcomere length and Ca²⁺] relationship was consistent as expected from the intact tissue, when it was measured soon after partial rupturing the cell membrane. Miniature fluctuations of individual sarcomere length were demonstrated during rest, which was augmented by the Ca²⁺ overload. The Ca²⁺] could be estimated from the measurements of sarcomere length during the positive staircase of contraction. The usefulness of the optical measurement of sarcomere pattern was indicated.