Figure 8.

Requirement for apical membrane cation channels and intracellular Ca²⁺ release in the phase 1 response to outward bowing. (A and B) The indicated channel blockers were added to the mucosal (A) or serosal (B) hemichamber and preincubated for 30 min at 37°C. The tissue was then bowed outward using a 20-gauge needle to fill the mucosal hemichamber at a 2 cm H₂O pressure head. (C) Tissue was pretreated with 2-APB or ryanodine for 1 h and then stretched as described in A and B. Alternatively, the apical solution was exchanged for one lacking Ca²⁺, and the tissue was stretched. In A-C untreated tissue served as a control and is reproduced from Figure 7. The experiments were repeated ≥3 times, and representative results are shown.