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Membrane ion channels as physiological targets for local Ca 2+ signalling
Author(s) -
Dmitri Gordienko,
Alexander Zholos,
T. B. Bolton
Publication year - 1999
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1046/j.1365-2818.1999.00599.x
Subject(s) - ryanodine receptor , bapta , biophysics , chemistry , carbachol , microbiology and biotechnology , calcium signaling , calcium , myocyte , second messenger system , patch clamp , voltage dependent calcium channel , receptor , transient receptor potential channel , cytoplasm , ion channel , confocal microscopy , biochemistry , biology , organic chemistry
Ionized calcium plays a central role as a second messenger in a number of physiologically important processes determining smooth muscle function. To regulate a wide range of cellular activities the mechanisms of subcellular calcium signalling should be very diverse. Recent progress in development of visible light‐excitable fluorescent dyes with high affinity for Ca 2+ (such as oregon green 488 BAPTA indicators, fluo‐3 and fura red) and confocal laser scanning microscopy provides an opportunity for direct visualization of subcellular Ca 2+ signalling and reveals that many cell function are regulated by the microenvironment within small regions of the cytoplasm (‘local control’ concept). Here confocal imaging is used to measure and locate changes in [Ca 2+ ] i on a subcellular level in response to receptor stimulation in visceral myocytes. We show that stimulation of muscarinic receptors in ileal myocytes with carbachol leading to activation of inositol 1,4,5‐trisphosphate receptors (IP 3 Rs) accelerates the frequency of spontaneous calcium sparks (discharged via ryanodine receptors, RyRs) and gives rise to periodic propagating Ca 2+ waves oscillating with a frequency similar to that of carbachol‐activated cationic current oscillations. Furthermore, by combining the whole‐cell patch clamp technique with simultaneous confocal imaging of [Ca 2+ ] i in voltage‐clamped vascular myocytes we demonstrate that calcium sparks may lead to the opening of either Ca 2+ ‐activated Cl − channels or Ca 2+ ‐activated K + channels, and the discharge of a spontaneous transient inward current (STIC) or a spontaneous transient outward current (STOC), respectively.