Stimulation of mucus secretion. (A) Mucus thickness of ileal explant mounted in the horizontal chamber. After mounting (time 0), mucus was removed from the CF mice by extensive aspiration before the measurement at 20 min. Mucus secretion was stimulated by basal perfusion with PGE₂ and CCh for 40 min (WT, CF, n = 4; WT CCh-PGE₂, n = 8; CF CCh-PGE₂, n = 7; **, P = 0.008). (B) Total mucus thickness after 40-min stimulation with CCh and PGE₂ and remaining thickness after aspiration of the mucus (n.s., nonsignificant; WT, n = 7; CF, n = 6; ***, P = 0.0006). (C) Quantification of Muc2 amount in secreted mucus from WT and CF ileum. The secreted mucus was collected, analyzed on an SDS-agarose-polyacrylamide composite gel, and visualized by SYPRO Ruby (top) and Alcian blue (bottom). A representative gel of four repeated experiments is shown. The Muc2 monomeric band is indicated by the arrows and has a molecular mass of ∼2.5 MD. (D) Intensity of the SYPRO Ruby staining of the Muc2 monomeric band in CF (n = 6) and WT (n = 6; four gels; **, P = 0.002). Data are presented as mean ± SEM.