Effect of SCFA on intracellular pH and intracellular pH regulation of guinea-pig caecal and colonic enterocytes and of HT29-19a monolayers

The response of the intracellular pH (pH(i), measured with BCECF) of the caecal and distal colonic epithelium of guinea pig and of monolayers of HT29 clone 19a cells on the addition of short chain fatty acids (SCFA) was assessed. Addition of SCFA to the luminal side of these cells had no major effect on pH(i), independent of whether the apical Na+/H+ exchange or the apical K+/H+ ATPase was inhibited or not. Addition of SCFA to the serosal side, on the other hand, caused a marked decrease of pH(i), followed by an effective regulation back to basal values, and after removal of the acid, the cells became alkalinized. Intracellular pH is mainly regulated by mechanisms in the basolateral membrane. The basolateral Na+/H+ exchanger and the Cl-/HCO3- exchanger were mainly responsible for pH(i) regulation. Inhibition studies are consistent with a NHE-1 type Na+/H+ exchanger in the basolateral membranes. The apical Na+/H+ exchanger of caecal enterocytes and in HT29 cells, and the apical K+/H+ ATPase in the apical membrane of the distal colon have no or little influence on pH(i) regulation. The comparison shows that the HT29-19a cell line is an adequate model for studying pH(i) phenomena of hind gut epithelial cells. (C) 1997 Elsevier Science Inc.