Differences in features of calcium transients between the nucleus and the cytosol in cultured heart muscle cells: analyzed by confocal microscopy.
We analyzed spatio-temporal characteristics of Ca2+ transients in the cytosol and the nucleus of cultured neonatal rat heart cells using confocal imaging with Indo-1 and Fluo-3. In resting heart muscle cells, nuclear [Ca2+] was maintained lower than the cytosolic level. The rise in nuclear [Ca2+], during either E-C coupling or propagation of the Ca2+ wave, began at the edge of the nucleus in the immediate vicinity of the rise in global or localized cytosolic [Ca2+], and spread inwardly. The rise in [Ca2+] was slower and smaller in the nucleus than in the cytosol. The decay in [Ca2+] was also slower in the nucleus than the cytosol, thereby reversing the initial [Ca2+] gradient between them. Caffeine markedly enhanced the rise in nuclear [Ca2+] while maintaining inward spreading. The heterogeneity of nuclear Ca2+ transients during cellular contractilities suggests that influx of Ca2+ from perinuclear stores into the nucleus plays a predominant role in the nuclear [Ca2+] rise. The results also indicated that spatio-temporal characteristics of Ca2+ transients are quite different between the nucleus and the cytosol, thereby suggesting that they are differentially regulated in the nucleus and the cytosol.
Minamikawa
T
T
Department of Pathology, Kyoto Prefectural University of Medicine, Japan.
Takahashi
A
A
Fujita
S
S
D000818:Animals; D000831:Animals, Newborn; D001692:Biological Transport / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D018613:Microscopy, Confocal; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D002110:Caffeine; D002118:Calcium