Figure 1

(A) MRP4 is localized to the basolateral membrane of acinar cells. MRP4 was determined by immunofluorescence as detailed in Materials and Methods. Immunofluorescence was concentrated in the basolateral membrane of acinar cells (left panel); negative control is shown (right panel). (B) MRP4 inhibition abolishes plasma cAMP increase evoked by secretin and ANF. Animals were pretreated with or without probenecid followed by infusion with secretin alone or with ANF; blood samples were withdrawn at 3, 5, 10, 15 and 30 min and cAMP was assessed by radioimmunoassay as described in Materials and Methods. Right panel: time course of cAMP after the different treatments. □, Control; ■, ANF; ▲ secretin; ●, secretin + ANF. Dotted lines represent the same groups treated with probenecid. Left panel: Area under each temporal curve. **p < 0.01 and ***p < 0.001 versus control; ^#p < 0.05 versus secretin; ^##p < 0.01 versus secretin + ANF. Scale bar, 20 µm.