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Flash photolysis studies of the localization of calcium release sites in rat parotid isolated acinar cells.
Author(s) -
Hassoni A A,
Gray P T
Publication year - 1994
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1994.sp020265
Subject(s) - chemistry , flash photolysis , biophysics , carbachol , inositol , calcium , patch clamp , inositol trisphosphate , membrane potential , muscarinic acetylcholine receptor , endocrinology , receptor , medicine , kinetics , biochemistry , biology , physics , organic chemistry , quantum mechanics , reaction rate constant
1. The temporal relationship between cytosolic free Ca2+ concentration ([Ca2+]i) and activation of membrane current responses in single rat parotid acinar cells has been examined. Activation of muscarinic receptors by carbachol (CCh) at ‐40 mV (midway between EK and ECl under our experimental conditions) frequently evoked biphasic current responses, application of 2 microM CCh leading to rapid activation of an inward current followed by a slower outward current. 2. Photochemical release of inositol 1,4,5‐trisphosphate (InsP3), from ‘caged’ InsP3, by a brief near‐UV flash, evoked similar biphasic current responses at ‐40 mV. In contrast, elevation of [Ca2+]i by photolysis of the caged calcium compound nitr‐5 at ‐40 mV activated only monophasic current responses. 3. These results can be explained by a model in which the InsP3‐sensitive Ca2+ release sites are localized at the luminal pole of the cell, combined with a relative preponderance of Ca(2+)‐activated Cl‐ channels at that pole, and a relative preponderance of Ca(2+)‐activated K+ channels at the basal end.