Fig. 1. Original recording of short-circuit current (I_sc) from leech integument adapted to high-salinity water. Increasing concentrations of ATP (in mmol l^-1) were added to the basolateral compartment at the indicated times. Note the weak decrease in I_sc in response to 10 mmol l^-1 ATP. The current sensitive to 100 µmol l^-1 amiloride was determined before superfusion with Na⁺-free Ringer's solution; periods of superfusion are shown below the recording.