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Nutrient modulation of polarized and sustained submembrane Ca 2+ microgradients in mouse pancreatic islet cells
Author(s) -
Quesada Ivan,
Martín Franz,
Soria Bernat
Publication year - 2000
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 - 10.1111/j.1469-7793.2000.t01-1-00159.x
Subject(s) - chemistry , cyclopiazonic acid , biophysics , membrane , calcium , membrane potential , intracellular , cytosol , diazoxide , analytical chemistry (journal) , endocrinology , biochemistry , insulin , chromatography , biology , organic chemistry , enzyme
1 The intracellular calcium concentration ([Ca 2+ ] i ) near the plasma membrane was measured in mouse pancreatic islet cells using confocal spot detection methods. 2 Whereas small cytosolic Ca 2+ gradients were observed with 3 mM glucose, a steeper sustained gradient restricted to domains beneath the plasma membrane (space constant, 0.67 μm) appeared with 16.7 mM glucose. 3 When the membrane potential was clamped with increasing K + concentrations (5, 20 and 40 mM), no [Ca 2+ ] i gradients were observed in any case. 4 Increasing glucose concentration (0, 5 and 16.7 mM) in the presence of 100 μM diazoxide, a K + channel opener, plus 40 mM K + induced steeper [Ca 2+ ] i gradients, confirming the role of membrane potential‐independent effects of glucose. 5 Prevention of Ca 2+ store refilling with 30 μM cyclopiazonic acid (CPA) or blockade of uniporter‐mediated Ca 2+ influx into the mitochondria with 1 μM carbonyl cyanide m‐ chlorophenyl hydrazone (CCCP) or 1 μM Ru‐360 significantly reduced the steepness of the 16.7 mM glucose‐induced [Ca 2+ ] i gradients. 6 Measured values of [Ca 2+ ] i reached 6.74 ± 0.67 μM at a distance of 0.5 μm from the plasma membrane and decayed to 0.27 ± 0.03 μM at a distance of 2 μm. Mathematically processed values at 0.25 and 0 μm gave a higher [Ca 2+ ] i , reaching 8.18 ± 0.86 and 10.05 ± 0.98 μM, respectively. 7 The results presented indicate that glucose metabolism generates [Ca 2+ ] i microgradients, which reach values of around 10 μM, and whose regulation requires the involvement of both mitochondrial Ca 2+ uptake and endoplasmic reticulum Ca 2+ stores.