Figure 2.

Effects of mucosal pH on the stimulation of Isc in T84 cells by guanylin and uroguanylin. T84 cells were cultured on collagen-coated membranes and mounted in Ussing chambers as described. At the arrows, the indicated concentrations of guanylin (Upper), uroguanylin (Lower), and E. coli ST-(5–17) were added to the apical reservoirs containing medium at either pH 5.5 (○) or pH 7.8 (•). For all experiments, the basolateral reservoir contained medium at pH 7.4. Data are representative experiments of at least five separate experiments performed with each peptide at the mucosal pH values of 5.5 and pH 7.8. Concentrations of guanylin and uroguanylin greater than 100 nM were not used in these experiments because they consumed excessive amounts of the peptides.