The two components in the shortening of unloaded ventricular myocytes: Their voltage dependence
In isolated myocytes from mammalian ventricles a fast and a slow component in the contractile response to depolarizing voltage clamp steps were identified. The potential dependence of the slow component was identical to the activation curve of iCa. The fast component, however, remained at its maximal amplitude at potentials positive to + 10 mV (up to + 100 mV), in which potential range iCa declined and eventually disappeared. The results suggest that the slow component may be activated by Ca + + entering through sarcolemmal Ca channels, whereas the fast component depends on Ca release from intracellular sites and may depend on both Cai and voltage.
Key wordscontraction calcium electro-mechanical coupling sarcomere length isotonic contraction
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- 2.Chapman RA (1983): Control of cardiac contractility at the cellular level. Am J Physiol H535 — H552Google Scholar
- 5.Fabiato A (1983): Calcium-induced release of calcium from the cardiac sarcoplasmic reticulum. Am J Physiol 245: Cl—C14Google Scholar
- 7.Isenberg G (1982): Ca entry and contraction as studied in isolated bovine ventricular myocytes. Z Naturforsch 37c: 502–512Google Scholar
- 11.Mascher D, Cruz A (1980): Electrical and mechanical responses of the guinea-pig ventricular muscle in the presence of histamine. XXVIII International Congress of Physiological Sciences. Budapest, 1980Google Scholar
- 12.Mullins LJ (1981): Ion transport in heart. Raven Press, New YorkGoogle Scholar