Figure 6.

Ca²⁺ sensitization induced by agonists and phorbol esters. Ca²⁺ sensitization of airway SMCs studied in Ca²⁺-permeabilized lung slices with 20 mM caffeine plus 25 µM ryanodine. (A) Representative phase-contrast images of a Ca²⁺-permeabilized lung slice showing an airway before (1) and after stimulation with 5-HT (2) or PMA (3) at the times indicated by the corresponding numbers in B. (B) Traces from two similar experiments showing the changes in airway lumen area during perfusion of caffeine plus ryanodine, 0.5 µM 5-HT, and 10 µM PMA (black trace) or 1 µM PDBu (gray trace) at the times indicated by the upper lines. (C) Summary of airway contractions induced by 5-HT, 50 mM of isosmotic KCl, PMA, or PDBu (mean ± SEM; eight airways from slices from four mice) in Ca²⁺-permeabilized lung slices obtained from experiments similar to that shown in B. *, different from baseline airway lumen area (P < 0.01). (D) Simultaneous changes in SMC [Ca²⁺]_i (top trace) and airway lumen area (bottom trace) during stimulation with caffeine plus ryanodine and after subsequent addition of PMA (added 20 s after washout of caffeine plus ryanodine). Traces in D are representative of four lung slices from three mice.