Thapsigargin inhibits the glucose-induced decrease of intracellular Ca2+ in mouse islets of Langerhans.
Stimulation of pancreatic islets of Langerhans with glucose results in changes in intracellular Ca2+ concentration ([Ca2+]i). With the use of mouse islets loaded with fura 2, the earliest glucose-induced alteration of [Ca2+]i was a pronounced decline in [Ca2+]i. This effect (phase 0) was evident 1 min after increasing extracellular glucose from 2 to 12 mM and was sustained for 3-5 min. Phase 0 was also observed when glucose was increased from 5 to 12 mM, indicating that it was not an experimental artifact resulting from substrate depletion. The [Ca2+]i-lowering effect of glucose was mimicked by D-glyceraldehyde but not by 2-deoxyglucose, pyruvate, glyburide, or 30 mM extracellular KCl. Mannoheptulose inhibited phase 0, whereas diazoxide, sodium azide, calmidazolium, or increasing extracellular [Ca2+] to 10 mM were all without effect. After the elevation of islet [Ca2+]i with 5 microM glyburide, 12 mM glucose caused a considerable transient decrease in [Ca2+]i. Under similar conditions, 5 mM caffeine attenuated phase 0, whereas 1 microM thapsigargin, a specific inhibitor of the sarcoplasmic and endoplasmic reticulum family of Ca(2+)-adenosinetriphosphatases (SERCA), almost completely inhibited any glucose-induced reduction of [Ca2+]i. These observations suggest that glucose causes an elevation of beta-cell SERCA activity triggered by factors generated during the cytosolic stages of glycolysis.
Roe
M W
MW
Department of Cell Physiology, Glaxo Research Institute, Research Triangle Park, North Carolina 27709.
Mertz
R J
RJ
Lancaster
M E
ME
Worley
J F
JF
Dukes
I D
ID
D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D002147:Calmodulin / Q000494:pharmacology; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005947:Glucose / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism*; D007515:Islets of Langerhans / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D013729:Terpenes / Q000494:pharmacology*; D019284:Thapsigargin
D002147:Calmodulin; D013729:Terpenes; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D005947:Glucose; D002118:Calcium