Glucose induces cytoplasmic Na+ oscillations in pancreatic beta-cells.
The cytoplasmic Na+ concentration ([Na+]i) was measured in individual mouse beta-cells and islet cell aggregates using the indicator SBFI. Small oscillations of [Na+]i were occasionally observed after raising glucose from 3 to 11 mM. Distinct oscillations with a frequency of 0.29 +/- 0.02 min-1 (n = 18) and amplitudes of 7.4 +/- 0.5 mM (n = 18) were obtained when also adding the Na+ channel agonist veratridine. The oscillations were counteracted by tetrodotoxin or by lowering the glucose concentration to 3 mM. Glucose failed to induce oscillations when increasing Na+ entry by co-transport with L-glycine or raising [Na+]i by blocking the Na/K pump with ouabain. The results indicate that glucose can induce oscillations of [Na+]i in pancreatic beta-cells, although this effect is usually less obvious due to activation of an efficient Na/K pump.
Grapengiesser
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Department of Medical Cell Biology, Uppsala University, Sweden. Eva.Grapengiesser@medcellbiol.uu.se
D000818:Animals; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology*; D005998:Glycine / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D008820:Mice, Obese; D009991:Oscillometry; D010042:Ouabain / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D062687:Sodium Channel Agonists; D026941:Sodium Channel Blockers; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors; D014701:Veratridine / Q000494:pharmacology
D062687:Sodium Channel Agonists; D026941:Sodium Channel Blockers; D013779:Tetrodotoxin; D010042:Ouabain; D014701:Veratridine; D012964:Sodium; D005947:Glucose; D005998:Glycine