Figure 5. Effects of basolateral UTP on luminal pH and fluid secretion.

Guinea-pig pancreatic ducts filled by micropuncture with a weakly buffered HCO₃⁻-free, Cl⁻-free solution containing 20 μm BCECF-dextran were initially superfused with a Cl⁻-free, Hepes-buffered bath solution. After 3 min this was switched to a Cl⁻-free, HCO₃⁻-buffered solution and, after a further 11 min, 10 nM secretin was applied via the bath. During the periods indicated, 1 μm UTP was applied via the bath in the absence or presence of 10 nM secretin. A, changes in luminal pH; B, changes in fluid secretory rate (one of four experiments).