Premium
Elementary Ca 2+ release events through IP3 receptors in the intact endothelium
Author(s) -
Sonkusare Swapnil,
Nelson Mark
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.626.4
Subject(s) - cyclopiazonic acid , egta , inositol trisphosphate receptor , biophysics , serca , chemistry , inositol , phospholipase c , endoplasmic reticulum , receptor , ryanodine receptor , intracellular , biochemistry , biology , calcium , enzyme , organic chemistry , atpase
Inositol triphosphate receptor (IP3R)‐mediated Ca 2+ release from endoplasmic reticulum is one of the most important mechanisms to increase intracellular Ca 2+ in all the cell types in the body. We have identified local IP3R‐mediated Ca 2+ signals (“pulsars”) at endothelial projections to the smooth muscle (Ledoux et al, PNAS, 2008), which are involved in the control of vascular function. The objective of this study was to elucidate the elementary properties of the IP3R Ca 2+ signals in the intact endothelium. The IP3R channel activity was optically recorded at 100 frames/second in slit‐open, resistance‐sized mesenteric arteries from mice using fluo‐8AM as a Ca 2+ indicator and EGTA‐AM to limit the spread of Ca 2+ . Step‐wise (quantal) changes in fluorescence were measured, which likely correspond to Ca 2+ flux through a single IP3R channel. Comparison of quantal levels for the voltage‐dependent Ca 2+ channel, IP3Rs and TRPV4 channel indicates an approximate single channel conductances to Ca 2+ of 3.5 pS, 14 pS and 35 pS respectively. The muscarinic receptor agonist carbachol (CCh, 10 mM) increased the activity of IP3R events, but did not alter the quantal amplitude. The IP3R events were eliminated by cyclopiazonic acid (SERCA inhibitor) and U73122 (phospholipase C inhibitor). Our results indicate that a IP3R‐mediated Ca 2+ pulsar reflects the opening of about 15 IP3R channels, and the presence of EGTA decreases this to about 7. These results may provide a unique method for studying the modulation of elementary properties of IP3Rs by physiological modulators in health and disease.