Effects of basal [Ca2+]i on calcium handling in Ca(2+)-overloaded rat cultured heart muscle cells.
To elucidate the relationship between intracellular free Ca2+ concentration ([Ca2+]i) and Ca(2+)-signalling by the sarcoplasmic reticulum (SR) in Ca(2+)-overloaded heart muscle cells, the direct effects of "basal" [Ca2+]i on calcium waves were investigated by altering the membrane potential. When basal inter-calcium wave (BCW) [Ca2+]i was maintained at a high level, (i) calcium waves showed more gradual and more rapidly suppressed increase in [Ca2+]-profile (P < 0.005), and (ii) calcium waves occurred at a significantly higher frequency and velocity (259% and 137%), than when low BCW [Ca2+]i was maintained. Similar investigations on inhibition of the Na(+)-Ca2+ exchanger, however, showed that membrane potential did not elicit direct effects on calcium waves. These results showed that the elevation of BCW [Ca2+]i per se directly influences Ca(2+)-signalling in heart muscle cells through non-equilibrated release-restoration Ca(2+)-handling by the SR.
Takahashi
A
A
Department of Pathology and Cell Regulation, Kyoto Prefectural University of Medicine, Japan.
Takamatsu
T
T
D000814:Aniline Compounds / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D008564:Membrane Potentials; D018613:Microscopy, Confocal; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D015398:Signal Transduction; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors; D014966:Xanthenes / Q000378:metabolism
D000814:Aniline Compounds; D019831:Sodium-Calcium Exchanger; D014966:Xanthenes; C059715:Fluo-3; D002118:Calcium