Regulation of Insulin Release Independent of Changes of Cytosolic Ca2+ Concentration

  • T. Tamagawa
  • H. Niki
  • A. Niki
  • I. Niki
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 211)


Although the central role of cytosolic Ca2+ in insulin release has been widely accepted mainly based on the 45Ca2+ flux studies20, it is not conclusive because of inability to measure changes of cytosolic Ca2+ concentration ([Ca2+]i) directly in the pancreatic β-cell. Recently, a method to estimate [Ca2+]i using a fluorescent Ca2+ indicator, quin 2, has been developed and applied to the pancreatic β-cell5,14,21,22 Some of the findings by this method do not accord with those observed in the 45Ca2+ flux studies22. Since quin 2 chelates calcium12 and may affect insulin release22, the data obtained using quin 2 should be interpreted with caution. Another approach to analyze the relationship between [Ca2+]i in the pancreatic β-cell and insulin release is to clamp [Ca2+]i at arbitrary levels. For this purpose, three methods have been developed in other cells2; i) microinjection of Ca or a suitable Ca-buffer into a cell, ii) intracellular dialysis or perfusion, and iii) permeabilization of the plasma membrane to permit extracellular Ca or Ca-EGTA buffers easy access to the intracellular environment. The first two methods are not suitable for small cells such as the pancreatic β-cell. The last method has been applied to pancreatic islets using high voltage electric discharge11,23 or digitonin treatment4,16. We describe here finding obtained using digitonin to permeabilize the cells in the islet.


Insulin Release Phorbol Ester Adrenal Medullary Cell Intact Islet Increase Insulin Release 
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Copyright information

© Plenum Press, New York 1986

Authors and Affiliations

  • T. Tamagawa
    • 1
    • 2
  • H. Niki
    • 1
    • 2
  • A. Niki
    • 1
    • 2
  • I. Niki
    • 1
    • 2
  1. 1.Department of Internal Medicine, School of DentistryAichigakuin UniversityChikusa-ku, Nagoya, 464Japan
  2. 2.Third Department of Internal Medicine, School of MedicineUniversity of NagoyaShowa-ku, Nagoya 466Japan

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