Tetracaine stimulates insulin secretion through the mobilization of Ca2+ from thapsigargin- and IP3-insensitive Ca2+ reservoir in pancreatic beta-cells.
The effect of tetracaine on 45Ca efflux, cytoplasmic Ca2+ concentration [Ca2+]i, and insulin secretion in isolated pancreatic islets and beta-cells was studied. In the absence of external Ca2+, tetracaine (0.1-2.0 mM) increased the 45Ca efflux from isolated islets in a dose-dependentOFF efflux caused by 50 mM K+ or by the association of carbachol (0.2 mM) and 50 mM K+. Tetracaine permanently increased the [Ca2+]i in isolated beta-cells in Ca2+-free medium enriched with 2.8 mM glucose and 25 microM D-600 (methoxiverapamil). This effect was also observed in the presence of 10 mM caffeine or 1 microM thapsigargin. In the presence of 16.7 mM glucose, tetracaine transiently increased the insulin secretion from islets perfused in the absence and presence of external Ca2+. These data indicate that tetracaine mobilises Ca2+ from a thapsigargin-insensitive store and stimulates insulin secretion in the absence of extracellular Ca2+. The increase in 45Ca efflux caused by high concentrations of K+ and by carbachol indicates that tetracaine did not interfere with a cation or inositol triphosphate sensitive Ca2+ pool in beta-cells.
Department of Biological Sciences, UNESP, Bauru, SP, Brazil.
J R
JR
Bosqueiro
E M
EM
Carneiro
S
S
Bordin
A C
AC
Boschero
D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013748:Tetracaine / Q000494:pharmacology*; D019284:Thapsigargin / Q000494:pharmacology
D000779:Anesthetics, Local; D004791:Enzyme Inhibitors; D007328:Insulin; D013748:Tetracaine; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium