Initiation and development of calcium waves in rat myocytes.
To understand the characteristics of asynchrony in spontaneously occurring increases in cytoplasmic calcium concentrations ([Ca2+]i) in the cardiac myocyte, we observed newly developed changes in regional [Ca2+]i after a physical injury to the sarcolemma. Myocytes were isolated from rat left ventricle and loaded with acetoxymethyl ester of fura-2. We analyzed dynamic changes in fluorescence images by video densitometry. After the injury was imposed, three types of responses were observed: 1) rapid contracture with steady increase in [Ca2+]i; 2) periodic development of a calcium wave; and 3) quiescence after the injury. In some myocytes with the second type of response, a sustained burst of calcium waves was observed. In myocytes in which multiple calcium waves are present simultaneously, a propagated wave can reset a cycle of wave generation at the wave focus. Waves disappear after their collision, which indicates the existence of a refractory period after the calcium transient. The wave originating from the focus with the fastest frequency dominates the whole cell. Thus dynamic changes in regional [Ca2+]i are asynchronous but are organized by the following principles: 1) a regional increase in [Ca2+]i can propagate; 2) a propagated calcium wave can reset a cycle of wave initiation at the focus; and 3) a regional calcium transient leaves a refractory period.
Ishide
N
N
First Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Miura
M
M
Sakurai
M
M
Takishima
T
T
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003720:Densitometry; D004594:Electrophysiology; D006321:Heart / Q000502:physiology; D008856:Microscopy, Fluorescence; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D009991:Oscillometry; D009994:Osmolar Concentration; D011677:Punctures; D051381:Rats; D012508:Sarcolemma
D002118:Calcium