Ca2+ stores in insulin-secreting cells: lack of effect of cADP ribose.
Ca2+ stores were examined in several insulin secreting cell types by measuring uptake and release of Ca2+ by permeabilised cells. In pancreatic islet cells or INS-1 cells, < 20% of the ATP-dependent, thapsigargin-sensitive Ca2+ pool could be released by saturating concentrations of inositol (1,4,5)P3 (InsP3). InsP3 released > 60% of the thapsigargin-sensitive Ca2+ pool in RINm5F cells. The total Ca2+ content of the thapsigargin-sensitive pool was similar in each of these cell types. Neither cADP ribose (cADPR; 1 microM) nor caffeine (10 mM) caused significant Ca2+ release from any of the permeabilised insulin-secreting cell preparations. ATP elicited similar increases in intracellular Ca2+ concentration ([Ca2+]i) in single, living INS-1 and RINm5F cells, and similar fold increases in InsP3 levels in cell populations. The Ca2+ ATPase inhibitor thapsigargin, added after ATP, caused smaller [Ca2+]i increases in RINm5F than in INS-1 cells. This is consistent with the presence of a smaller InsP3-sensitive Ca2+ pool in living INS-1 cells. The data indicate that InsP3 receptors are present in only a small subfraction of the Ca2+ ATPase-containing Ca2+ stores in INS-1 and pancreatic beta-cells, and that cADP ribose/caffeine-sensitive Ca(2+)-induced Ca2+ release channels may be entirely absent from this endocrine cell type.
Rutter
G A
GA
Department of Medicine, University of Geneva, Switzerland.
Theler
J M
JM
Li
G
G
Wollheim
C B
CB
D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000032:analysis* / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002460:Cell Line; D002463:Cell Membrane Permeability / Q000187:drug effects; D036563:Cyclic ADP-Ribose; D004305:Dose-Response Relationship, Drug; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D007515:Islets of Langerhans / Q000737:chemistry* / Q000166:cytology* / Q000378:metabolism; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
D015220:Calcium Channels; D013729:Terpenes; D036563:Cyclic ADP-Ribose; D000246:Adenosine Diphosphate Ribose; D002110:Caffeine; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium