Basic properties of a novel ryanodine-sensitive, caffeine-insensitive calcium-induced calcium release mechanism in permeabilised human vascular smooth muscle cells.
The efflux of 45Ca2+ from preloaded intracellular stores of saponin-permeabilised human uterine artery smooth muscle cultured cells was used to study the mechanisms underlying Ca2+ release from the sarcoplasmic reticulum (SR). The present paper demonstrates directly a functional Ca2+ release mechanism that is dependent on an increase in free Ca2+ (100 nM-30 microM) and is completely inhibited by 20 microM Ruthenium red. The amount of Ca2+ released at 30 microM free Ca2+ was reduced by approximately 50% compared to the release at 10 microM. This Ca(2+)-induced Ca2+ release (CICR) mechanism was not sensitive to caffeine. Exposure of cells to low free Ca(2+)-containing solutions (10 nM) indicated that a component of the CICR mechanism may be functional at basal free Ca2+ levels of 100 nM. Application of ryanodine (0.1-100 microM) induced 45Ca2+ efflux from the sarcoplasmic reticulum and this release was also inhibited by 20 microM Ruthenium red.
Lynn
S
S
Department of Physiological Sciences, Medical School, University of Newcastle upon Tyne, UK.
Gillespie
J I
JI
D000328:Adult; D001158:Arteries / Q000378:metabolism*; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D012430:Ruthenium Red / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology*
D012430:Ruthenium Red; D012433:Ryanodine; D002110:Caffeine; D002118:Calcium