Figure 4. Pulse protocol.

Example of an experiment where the basolateral osmolality (π) was reduced to 140 mosmol (kg H₂O)⁻¹. The basolateral compartment was continuously perfused at a rate of 5 ml min⁻¹ with isosmotic or hyposmotic solutions. The perfusion was interrupted during 90 s intervals after 5 ml of the LL-containing solutions had passed the basolateral bath. R_ATP was calculated from the slope of increase in luminescence and the calibration factor listed in Table 1. The sensitivity and high dynamic range of the photon counter enabled the determination of R_ATP in iso- as well as in hyposmotic conditions.