title: Spontaneous versus triggered contractions of "calcium-tolerant" cardiac cells from the adult rat ventricle.
abstract: Cardiac cells were isolated from the adult rat ventricle by an enzymatic treatment. The cells considered intact were quiescent in the presence of 2.5 mM free Ca2+ but responded to an electrical stimulation by an homogeneous and brief contraction. When the procedure failed, spontaneous cyclic contractions occurred. Often they propagated as a wave from an intercalated disk, and the tension recording showed several components in each contraction. Electrical stimulation at a frequency higher than that of the spontaneous contractions induced synchronous activation with a single component of the tension. Experiments in skinned cardiac cells suggested that the spontaneous cyclic contractions observed in enzymatically separated cardiac cells are caused by a spontaneous cyclic release of Ca2+ from the sarcoplasmic reticulum (SR). This spontaneous release requires a Ca2+ overload of the SR. Its mechanism is different from that of the Ca2+-induced release of Ca2+, which is elicited by a rapid increase of [free Ca2+] at the outer surface of the SR of a previously quiescent skinned cell.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002469:Cell Separation / Q000379:methods; D004558:Electric Stimulation; D004576:Electromyography; D006352:Heart Ventricles / Q000166:cytology; D008866:Microsurgery; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000166:cytology*; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013997:Time Factors; D016276:Ventricular Function
chemical_list: D002118:Calcium