Na⁺/HCO₃^-cotransporter is expressed on β and α cells during rat pancreatic development

Abstract

AIMTo determine the expression and localization of the electrogenic Na+/HCO3- cotransporter (NBC1) in rat pancreas during development.METHODSThe rat pancreas from postnatal and embryos removed from the uterus of pregnant rats that had been sacrificed by CO2 asphyxiation were used. Rat pancreas from embryonic day (E) 15.5 and E18.5 rat embryos was isolated under a stereomicroscope. Rat pancreas from postnatal (P) days 0, 7, 14, 21 and adult was directly isolated by the unaided eye. The RT-PCR analysis of the NBC1 specific region on rat pancreas tissues from different developmental stages. The two antibodies which target the NBC1 common COOH-terminal region and NH2-terminal region detected a clear band of about 145 kDa in the Western blot analysis. The localization of NBC1 was examined by immuno-fluorescence detection.RESULTSThe results revealed the first peak of NBC1 expression at E18.5 and the second peak at P14. Meanwhile, the low NBC1 expression occurred at P7 and adult stages. Our results demonstrated, for the first time, the presence of NBC1 in the plasma membrane of β and α cells, as well as in the basolateral membrane of acinar cells of the rat pancreas at different stages of development.CONCLUSIONThe data strongly suggests that NBC1 is diversely expressed in the pancreas at different developmental stages, where it may exert its functions in pancreatic development especially islet cell growth through HCO3- transport and pH regulation.

Role of cAMP in Double Switch of Glucagon Secretion

“…Lastly, transport of bicarbonate in mammals is mostly facilitated by Cl − /HCO 3 − exchangers (AEs), Na + -coupled transporters (NBCs) [ 51 , 52 ], and they are also expressed in islet cells [ 53 , 54 ]. While transport dynamics of bicarbonate might be relatively complex, involving membrane potential (electrogenic transporters) and concentrations of co-transported ions, we again assume a simplified gradient-dependent removal of bicarbonate: where is the corresponding constant, [HCO 3 − ] in is the intracellular bicarbonate concentration, and [HCO 3 − ] bas is the extracellular (constant) bicarbonate concentration.…”