Microfluorometric analysis of Cl- permeability and its relation to oscillatory Ca2+ signalling in glucose-stimulated pancreatic beta-cells.
The cytoplasmic concentrations of Cl-([Cl-]i) and Ca2+ ([Ca2+]i) were measured with the fluorescent indicators N-(ethoxycarbonylmethyl)-6-methoxyquinilinum bromide (MQAE) and fura-2 in pancreatic beta-cells isolated from ob/ob mice. Steady-state [Cl-]i in unstimulated beta-cells was 34 mM, which is higher than expected from a passive distribution. Increase of the glucose concentration from 3 to 20 mM resulted in an accelerated entry of Cl- into beta-cells depleted of this ion. The exposure to 20 mM glucose did not affect steady-state [Cl-]i either in the absence or presence of furosemide inhibition of Na+, K+, 2 Cl- co-transport. Glucose-induced oscillations of [Ca2+]i were transformed into sustained elevation in the presence of 4,4' diisothiocyanato-dihydrostilbene-2,2'-disulfonic acid (H2DIDS). A similar effect was noted when replacing 25% of extracellular Cl- with the more easily permeating anions SCN-, I-, NO3- or Br-. It is concluded that glucose stimulation of the beta-cells is coupled to an increase in their Cl- permeability and that the oscillatory Ca2+ signalling is critically dependent on transmembrane Cl- fluxes.
Eberhardson
M
M
Department of Medical Cell Biology, Uppsala University, Biomedicum Box 571, SE-751 23, Uppsala, Sweden.
Patterson
S
S
Grapengiesser
E
E
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D000838:Anions / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects*; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism* / Q000494:pharmacology; D004553:Electric Conductivity; D005453:Fluorescence; D005470:Fluorometry / Q000379:methods; D016257:Fura-2; D005665:Furosemide / Q000494:pharmacology; D005711:Gallopamil / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D008817:Mice, Mutant Strains; D009765:Obesity / Q000235:genetics; D011806:Quinolinium Compounds
D000838:Anions; D002121:Calcium Channel Blockers; D002712:Chlorides; D011806:Quinolinium Compounds; C085493:N-(ethoxycarbonylmethyl)-6-methoxyquinolinium; D005711:Gallopamil; C018564:dihydro-DIDS; D005665:Furosemide; D005947:Glucose; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium; D016257:Fura-2