Figure 3.HCO3 - secretion in isolated rabbit duodenal mucosae in an Ussing-chamber setup. Control conditions (A): stimulation with 8-Br-cAMP. Stimulation with 8- Br-cAMP in the presence of 1 mM DIDS (B), 1 mM acetaz olamide (C), acetazolamide+DIDS (D), and Hoechst 642+DIDS (E)..