Behavior of Ca(2+) waves in multicellular preparations from guinea pig ventricle.
Ca(+) waves have been implicated in Ca(2+) overload-induced cardiac arrhythmias. To deepen understanding of the behavior of Ca(2+) waves in a multicellular system, consecutive two-dimensional Ca(2+) images were obtained with a confocal microscope from surface cells of guinea pig ventricular papillary muscles loaded with fluo 3 or rhod 2. In intact muscles, no Ca(2+) waves were detected under the resting condition, whereas they were frequently observed during the rest immediately after high-frequency stimulations where cytoplasmic Ca(2+) concentration and Ca(2+) stored in the sarcoplasmic reticulum (SR) were gradually decreasing. The intervals of Ca(2+) waves increased as they occurred later, their amplitudes and velocities remaining unchanged. A SERCA inhibitor reversibly prolonged the wave intervals. In Na(+)-free/Ca(2+)-free medium where neither Ca(2+) influx nor Na(+)/Ca(2+) exchange took place, recurrent Ca(2+) waves emerged at constant intervals in each cell. These results are consistent with the conclusion that the loading level of the SR is critical for induction of Ca(2+) waves. Each cell independently exhibited its own regular rhythm of Ca(2+) wave with a distinct interval. These waves propagated in either direction along the longitudinal axis within a muscle cell, but seldom beyond the cell boundary. In contrast, in partially damaged muscles that showed spontaneous Ca(2+) waves at rest in normal Krebs solution, their propagation often was unidirectional, decreasing in frequency. In these cases, however, Ca(2+) waves rarely moved beyond the cellular boundary. The gradient of the cytoplasmic Ca(2+) concentration was suggested to be the cause of the one-way propagation.
Kurebayashi
Nagomi
N
Department of Pharmacology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan. nagomik@med.juntendo.ac.jp
Yamashita
Haruyo
H
Nakazato
Yuji
Y
Daida
Hiroyuki
H
Ogawa
Yasuo
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004558:Electric Stimulation; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000378:metabolism; D010210:Papillary Muscles / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D012964:Sodium / Q000378:metabolism
D012964:Sodium; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D002118:Calcium