Cytosolic Ca2+ gradients triggering unidirectional fluid secretion from exocrine pancreas.
Exocrine gland cells secrete Cl(-)-rich fluid when stimulated by neurotransmitters or hormones. This is generally ascribed to a rise in cytosolic Ca2+ concentration ([Ca2+]i), which leads to activation of Ca2(+)-dependent ion channels. A precise understanding of Cl- secretion from these cells has been hampered by a lack of knowledge about the spatial distribution of the Ca2+ signal and of the Ca2(+)-dependent ion channels in the secreting epithelial cells. We have now used the whole-cell patch-clamp method and digital imaging of [Ca2+]i to examine the response of rat pancreatic acinar cells to acetylcholine. We found a polarization of [Ca2+]i elevation and ion channel activation, and suggest that this comprises a novel 'push-pull' mechanism for unidirectional Cl- secretion. This mechanism would represent a role for cytosolic Ca2+ gradients in cellular function. The cytosolic [Ca2+]i gradients and oscillations of many other cells could have similar roles.
Max-Planck-Institut für biophysikalische Chemie, Göttingen, Germany.
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H
Kasai
G J
GJ
Augustine
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D004553:Electric Conductivity; D005456:Fluorescent Dyes; D016257:Fura-2; D007473:Ion Channels / Q000502:physiology; D008564:Membrane Potentials; D008565:Membrane Proteins / Q000502:physiology; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism*; D010189:Pancreatic Juice / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D015398:Signal Transduction / Q000502:physiology
D018118:Chloride Channels; D002712:Chlorides; D005456:Fluorescent Dyes; D007473:Ion Channels; D008565:Membrane Proteins; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium; D016257:Fura-2