Figure 4. Effects of basolateral ATP 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 6 min, 10 nM secretin was applied via the bath. During the periods indicated, 1 μm ATP 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 five experiments).C, concentration-dependent effects of basolateral ATP on the fluid secretory rate evoked by 10 nM secretin. Increasing concentrations of ATP (0.1 μm and 1 μm) were applied successively via the bath during stimulation with 10 nM secretin. Data are means ±s.e.m. of four experiments.