Z Gastroenterol 2009; 47 - A12
DOI: 10.1055/s-0029-1223991

Characterization of the acid/base transporters in human gastric myofibroblasts

M Czepan 1, Z Rakonczay 1, A Schnur 1, G Lazar 2, Z Simonka 2, L Tiszlavicz 3, I Nemeth 3, V Venglovecz 4, A Varro 5, J Lonovics 1, T Wittmann 1, P Hegyi 1
  • 1University of Szeged, 1st Department of Medicine
  • 2Department of Surgery
  • 3Department of Pathology
  • 4Department of Pharmacology and Pharmacotherapy
  • 5University of Liverpool, Department of Physiology

Background &Aims: Myofibroblasts are found subepithelially in many mucosal surfaces throughout the gastrointestinal tract. They play a central role in wound healing, repair of the extracellular matrix, epithelial proliferation and oncogenesis. Due to the large variety of functions, they can face different acid or alkali loads which can come either from its intrinsic metabolism or from an external source. Our aim was to characterize the intracellular pH (pHi) regulation of human myofibroblasts.

Methods: Myofibroblasts were isolated from human gastric resection tissue. The cells were stained for alpha smooth muscle actin and vimentin from each preparation to monitor the purity. Myofibroblasts were loaded with the pH sensitive fluorescent dye BCECF-AM. The changes of fluorescence intensity were measured by an Olympus CellR imaging system. The basic acid/base transport mechanisms were studied by: 1) removing or replacing different ions (Na+, HCO3-, Cl-, K+) in the extracellular solution, 2) generating acid or alkali load using the ammonium pulse technique.

Results: We found that the resting pHi of gastric myofibroblasts is 7.21±0.02. Administration of standard HCO3-/CO2 solution to the cells caused a quick acidification suggesting a rapid CO2 diffusion into the cells. This was followed by a Na+ dependent HCO3- influx suggesting an active Na+/HCO3- contransporter. Cl- removal from the extracellular standard HCO3-/CO2 solution caused an alkalization which was very much diminished in HCO3- free solution. In addition, the recovery from alkali load (evoked by the ammonium pulse technique) was dependent on both HCO3- and Cl- availability suggesting a functionally active anion exchanger on the cells. The recovery from acid load was totally dependent on Na+ but only partially on HCO3-.

Conclusions: Human gastric myofibroblasts express functionally active Na+/H+ and Cl-/HCO3- exchangers and Na+/HCO3- cotransporter but no proton pump.

This work was supported by OTKA, MTA and NKTH.