title: Expression of the electrogenic Na+-HCO3--cotransporters NBCe1-A and NBCe1-B in rat pancreatic islet cells.
abstract: It was recently proposed that, in rat pancreatic islets, the production of bicarbonate accounts for the major fraction of the carbon dioxide generated by the oxidative catabolism of nutrient insulin secretagogues. In search of the mechanism(s) supporting the membrane transport of bicarbonate, the possible role of the electrogenic Na(+)-HCO(3) (-)-cotransporters NBCe1-A and NBCe1-B in rat pancreatic islet cells was investigated. Expression of NBCe1-A and NBCe1-B in rat pancreatic islet cells was documented by RT-PCR, western blotting, and immunocytochemistry. The latter procedure suggested a preferential localization of NBCe1-B in insulin-producing cells. Tenidap (3-100 microM), previously proposed as an inhibitor of NBCe1-A-mediated cotransport in proximal tubule kidney cells, caused a concentration-related inhibition of glucose-stimulated insulin secretion. It also inhibited 2-ketoisocaproate-induced insulin release and to a relatively lesser extent, the secretory response to L: -leucine. Tenidap (50-100 microM) also inhibited the metabolism of D: -glucose in isolated islets, increased (22)Na net uptake by dispersed islet cells, lowered intracellular pH and provoked hyperpolarization of plasma membrane in insulin-producing cells. This study thus reveals the expression of the electrogenic Na(+)-HCO(3) (-)-cotransporters NBCe1-A and NBCe1-B in rat pancreatic islet cells, and is consistent with the participation of such transporters in the process of nutrient-stimulated insulin secretion.
authors.affiliation: Laboratory of Biological Chemistry and Nutrition, Université Libre de Bruxelles, Brussels, Belgium.
authors.forename: Muhammad S
authors.initials: MS
authors.lastname: Soyfoo
authors.forename: Nurdan
authors.initials: N
authors.lastname: Bulur
authors.forename: Myrna
authors.initials: M
authors.lastname: Virreira
authors.forename: Karim
authors.initials: K
authors.lastname: Louchami
authors.forename: Pascale
authors.initials: P
authors.lastname: Lybaert
authors.forename: Raphael
authors.initials: R
authors.lastname: Crutzen
authors.forename: Jason
authors.initials: J
authors.lastname: Perret
authors.forename: Christine
authors.initials: C
authors.lastname: Delporte
authors.forename: Eleni
authors.initials: E
authors.lastname: Roussa
authors.forename: Frank
authors.initials: F
authors.lastname: Thevenod
authors.forename: Len
authors.initials: L
authors.lastname: Best
authors.forename: Allen P
authors.initials: AP
authors.lastname: Yates
authors.forename: Willy J
authors.initials: WJ
authors.lastname: Malaisse
authors.forename: Abdullah
authors.initials: A
authors.lastname: Sener
authors.forename: Renaud
authors.initials: R
authors.lastname: Beauwens
mesh_terms: D000818:Animals; D015870:Gene Expression; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D008564:Membrane Potentials / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D027982:Sodium-Bicarbonate Symporters / Q000235:genetics* / Q000378:metabolism; D014018:Tissue Distribution
chemical_list: D007328:Insulin; D020033:Protein Isoforms; C422004:Slc4a4 protein, rat; D027982:Sodium-Bicarbonate Symporters; D012964:Sodium; D005947:Glucose