Subcellular distribution of Ca2+ release channels underlying Ca2+ waves and oscillations in exocrine pancreas.
Agonists trigger Ca2+ waves and oscillations in exocrine gland cells. Our confocal Ca2+ imaging revealed three distinct phases during the Ca2+ waves in the rat pancreatic acinar cell. Rises in Ca2+ concentration were initiated at a small trigger zone, or T zone, in the granular area; then, Ca2+ waves rapidly spread within the area and, at high agonist concentrations, propagated slowly toward the basal pole. Injection of inositol 1,4,5-trisphosphate (IP3) or Ca2+ from patch pipettes demonstrated the presence of high sensitivity IP3 receptors at the T zone, Ca(2+)-induced Ca2+ release channels in the granular area, and low sensitivity IP3 receptors in the basal area. The IP3 receptors at the T zone appeared to generate autonomous Ca2+ spikes and to initiate patterned Ca2+ oscillations. Thus, heterogeneous cytosolic localization of Ca2+ release channels plays a key role in Ca2+ waves and oscillations.
Department of Physiology, Faculty of Medicine, University of Tokyo, Japan.
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Kasai
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Li
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Miyashita
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D008856:Microscopy, Fluorescence; D010179:Pancreas / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D015290:Second Messenger Systems; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors
D015220:Calcium Channels; D000109:Acetylcholine; D002118:Calcium