Role of Na+-H+-antiport in restitution of isolated guinea pig gastric epithelium after superficial injury

In addition to its pH(i) regulatory function Na+-H+-antiport is also involved in volume regulation of epithelial cells, particularly in neutral conditions. It is also known that the antiport is activated after ligand binding following growth factor receptor activation. The aim of the present study was to evaluate the role of the antiport in restitution of gastric mucosa and whether its activity is dependent on the type of superficial injury. Therefore the fundic epithelium of guinea pig stomach was perfused in an Ussing chamber in neutral conditions. Na+-H+- and Cl--HCO3--antiports were inhibited with 1.0 mM amiloride, 1.0 mM SITS, or with HCO3- removal and Na+-K+-2Cl(2-)-cotransporter with 0.3 M furosemide during 4 hr of restitution after superficial injury induced either by 1.25 M NaCl or by 1.0% Triton. Luminal exposure of the epithelium to amiloride had no effect on restitution but serosal application abolished the process completely. The inhibitory effect of amiloride was similar after both NaCl and Triton injury. The inhibition of Cl--HCO3--antiport with SITS interfered with the process as well, while HCO3- removal had no significant inhibitory effect, nor did the inhibition of Na+-K+-2Cl(-)-cotransporter. The morphologic findings were in accordance with the electrophysiologic measurements in each pair of tissues. It is concluded that the Na+-H+-antiport is essential for the epithelial cells during restitution even in neutral conditions, but a functional Cl--HCO3--antiport is also required. The activity of Na+-H+-antiport is sensitive to basolateral amiloride and is necessary regardless of the type of chemical injury.