Role of intracellular stores in the regulation of rhythmical [Ca2+]i changes in interstitial cells of Cajal from rabbit portal vein.
Interstitial cells of Cajal (ICCs) freshly isolated from rabbit portal vein and loaded with the Ca(2+)-sensitive indicator fluo-3 revealed rhythmical [Ca(2+)](i) changes occurring at 0.02-0.1 Hz. Each increase in [Ca(2+)](i) originated from a discrete central region of the ICC and propagated as a [Ca(2+)](i) wave towards the cell periphery, but usually became attenuated before reaching the ends of the cell. In about 40% of ICCs each rhythmical change in [Ca(2+)](i) consisted of an initial [Ca(2+)](i) increase (phase 1) followed by a faster rise in [Ca(2+)](i) (phase 2) and then a decrease in [Ca(2+)](i) (phase 3); the frequency correlated with the rate of rise of [Ca(2+)](i) during phase 1, but not with the peak amplitude. Rhythmical [Ca(2+)](i) changes persisted in nicardipine, but were abolished in Ca(2+)-free solution as well as by SK&F96365, cyclopiazonic acid, thapsigargin, 2-APB, xestospongin C or ryanodine. Intracellular Ca(2+) stores visualised with the low-affinity Ca(2+) indicator fluo-3FF were found to be enriched with ryanodine receptors (RyRs) detected with BODIPY TR-X ryanodine. Rhythmical [Ca(2+)](i) changes originated from a perinuclear S/ER element showing the highest RyR density. Immunostaining with anti-TRPC3,6,7 antibodies revealed the expression of these channel proteins in the ICC plasmalemma. This suggests that these rhythmical [Ca(2+)](i) changes, a key element of ICC pacemaking activity, result from S/ER Ca(2+) release which is mediated via RyRs and IP(3) receptors and is modulated by the activity of S/ER-Ca(2+)-ATPase and TRP channels but not by L-type Ca(2+) channels.
Harhun
Maksym
M
Division of Basic Medical Sciences, Ion Channels and Cell Signalling Centre, St. George's, University of London, Cranmer Terrace, London SW 17 0RE, UK. m.harhun@sgul.ac.uk
Gordienko
Dmitri
D
Kryshtal
Dmytro
D
Pucovský
Vladimír
V
Bolton
Thomas
T
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism*; D018613:Microscopy, Confocal; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000502:physiology; D010507:Periodicity; D011169:Portal Vein / Q000166:cytology* / Q000378:metabolism / Q000502:physiology; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000032:analysis; D012519:Sarcoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism; D050051:Transient Receptor Potential Channels / Q000032:analysis
D019837:Ryanodine Receptor Calcium Release Channel; D050051:Transient Receptor Potential Channels; D002118:Calcium