Agonist-induced localized Ca2+ spikes directly triggering exocytotic secretion in exocrine pancreas

Y. Maruyama, G. Inoola, Y. X. Li, Y. Miyashita, H. Kasai

Research output: Contribution to journalArticlepeer-review

94 Citations (Scopus)

Abstract

We investigated how agonist-induced patterned rises in cytosolic Ca2+ concentration ([Ca2+](i)) regulate exocytotic secretion in the rat pancreatic acinar cell. The distribution of [Ca2+]; was visualized with a confocal microscope, which revealed that a Ca2+ ionophore, A23187, induced slow and homogeneous [Ca2+](i) rises, while acetylcholine (ACh) always triggered primary Ca2+ spikes at the granular area which bears secretory granules. Secretion was monitored by measuring capacitance with the patch clamp method. Errors in the estimates of membrane capacitance (C) due to changes in conductance (G) were experimentally as well as theoretically evaluated to be one-tenth of the actual signals. We found that A23187 raised G without changing C at a low concentration, while it triggered asynchronous rises in G and C with lags in C, at a high concentration. By contrast, ACh triggered simultaneous rapid rises in G and C. Our results support the hypothesis that exocytotic secretion is less sensitive to Ca2+ than to ion channels and is directly caused by agonist-induced primary Ca2+ spikes at the granular area. It is therefore suggested that spatio-temporal patterns of Ca2+ oscillations could play a key role in exocytotic secretion from the exocrine acinar cell.

Original languageEnglish
Pages (from-to)3017-3022
Number of pages6
JournalEMBO Journal
Volume12
Issue number8
DOIs
Publication statusPublished - 1993

Keywords

  • Ca
  • Capacitance measurement
  • Confocal microscope
  • Imaging
  • Patch clamp
  • Secretion

ASJC Scopus subject areas

  • Neuroscience(all)
  • Molecular Biology
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

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