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Ryanodine receptors of pancreatic β‐cells mediate a distinct context‐dependent signal for insulin secretion
Author(s) -
Bruton Joseph D.,
Lemmens Raf,
Shi ChunLiang,
PerssonSjögren Solveig,
Westerblad Håkan,
Ahmed Masroor,
Pyne Nigel J.,
Frame Mhairi,
Furman Brian L.,
Islam Md. Shahidul
Publication year - 2003
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.02-0481fje
Subject(s) - caffeine , ryanodine receptor , forskolin , endocrinology , medicine , secretion , receptor , stimulation , context (archaeology) , insulin , chemistry , biology , paleontology
The ryanodine (RY) receptors in β‐cells amplify signals by Ca 2+ ‐induced Ca 2+ release (CICR). The role of CICR in insulin secretion remains unclear in spite of the fact that caffeine is known to stimulate secretion. This effect of caffeine is attributed solely to the inhibition of cAMP‐phosphodiesterases (cAMP‐PDEs). We demonstrate that stimulation of insulin secretion by caffeine is due to a sensitization of the RY receptors. The dose‐response relationship of caffeine‐induced inhibition of cAMP‐PDEs was not correlated with the stimulation of insulin secretion. Sensitization of the RY receptors stimulated insulin secretion in a context‐dependent manner, that is, only in the presence of a high concentration of glucose. This effect of caffeine depended on an increase in [Ca 2+ ] i . Confocal images of β‐cells demonstrated an increase in [Ca 2+ ] i induced by caffeine but not by forskolin. 9‐Methyl‐7‐bromoeudistomin D (MBED), which sensitizes RY receptors, did not inhibit cAMP‐PDEs, but it stimulated secretion in a glucose‐dependent manner. The stimulation of secretion by caffeine and MBED involved both the first and the second phases of secretion. We conclude that the RY receptors of β‐cells mediate a distinct glucose‐dependent signal for insulin secretion and may be a target for developing drugs that will stimulate insulin secretion only in a glucose‐dependent manner.