Caffeine releases a glucose-primed endoplasmic reticulum Ca2+ pool in the insulin secreting cell line INS-1.
Caffeine mobilized an intracellular Ca2+ pool in intact fura-2-loaded INS-1 cells in suspension exposed to high (16 mM) [glucose], while a minor effect was observed with low (2 mM) [glucose]. Cells were kept in a medium containing diaxozide or no Ca2+ to prevent the influx of extracellular Ca2+. The caffeine-sensitive intracellular Ca2+ pool was within the endoplasmic reticulum since it was depleted by the inhibitor of the reticular Ca2+ pumps thapsigargin and the InsP3-dependent agonist carbachol. No effect of caffeine was observed in the parent glucose-insensitive RINmF5 cells. In microsomes from INS-1 but not RINmF5 cells, the type 2 ryanodine receptor was present as revealed by Western blotting. It was concluded that the endoplasmic reticulum of INS-1 cells possesses caffeine-sensitive type 2 ryanodine receptors Ca2+ channels.
Gamberucci
A
A
Istituto di Patologia Generale, Università di Siena, Italy.
Fulceri
R
R
Pralong
W
W
Bánhegyi
G
G
Marcolongo
P
P
Watkins
S L
SL
Benedetti
A
A
D000818:Animals; D002110:Caffeine / Q000378:metabolism* / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D003981:Diazoxide / Q000494:pharmacology; D004594:Electrophysiology; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D007328:Insulin; D011817:Rabbits; D019284:Thapsigargin / Q000494:pharmacology
D007328:Insulin; D002110:Caffeine; D019284:Thapsigargin; D002217:Carbachol; D005947:Glucose; D003981:Diazoxide; D002118:Calcium