Fig. 2. Effect of bafilomycin A₁ on acid secretion by intact turtle bladders. Dose—response inhibition curve. Turtle urinary bladders were mounted in Ussing-type chambers and bathed in Na/Cl/HCO₃ Ringer's solution. The serosal solution contained 0.2 mmol l^-1 ouabain. Under these conditions the short-circuit current across the tissue approximates the rate of net acid-base transport and is typically oriented serosal-side negative (acid secretion; see Materials and methods). Baseline acid secretion (100 %) was -12.0±4.3 µA (per area of chamber, 1.43 cm²) (N=4). Bafilomycin A₁ in DMSO vehicle was added in the luminal solution to the concentrations indicated and the short-circuit current allowed to stabilize after each addition. The final concentration of DMSO never exceeded 0.3 %.