Dual effect of glucose on cytoplasmic free Ca2+ concentration and insulin release reflects the beta-cell being deprived of fuel.
Influence of basal glucose concentration on the response evoked by subsequent stimulation with the sugar, was evaluated by investigating changes in free cytoplasmic Ca2+ concentration, [Ca2+]i, and insulin release, using beta-cells isolated from obese hyperglycemic mice. When increasing the glucose concentration from 0 to either 11 or 20 mM, there was a transient decrease in both [Ca2+]i and insulin release. The decrease was followed by a pronounced increase in both of the parameters. When increasing the basal glucose concentration, the initial decrease gradually disappeared, being abolished already at 5 mM of the sugar and the subsequent increase appeared more rapidly. It is suggested that the observed decrease in [Ca2+]i and thereby insulin release reflects a phenomenon associated with fuel deprived beta-cells.
Nilsson
T
T
Department of Medical Cell Biology, University of Uppsala, Sweden.
Arkhammar
P
P
Berggren
P O
PO
D000818:Animals; D001572:Benzofurans; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism; D005260:Female; D016257:Fura-2; D005947:Glucose / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051379:Mice; D008820:Mice, Obese
D001572:Benzofurans; D007328:Insulin; D005947:Glucose; D002118:Calcium; D016257:Fura-2