Figure 6.

Caffeine but not 8-Br-cAMP inhibits CCE in canine PASMCs. (A) Effect of extracellular Ca²⁺ removal, 10 μM CPA, sequential exposure to 10 mM caffeine and 10 μM 5-HT on cytosolic [Ca²⁺] with extracellular Ca²⁺ re-addition. Effects of (B) 1 mM 8-Br-cAMP and (C) 10 mM caffeine on the cytosolic [Ca²⁺] with depletion of the sarcoplasmic reticulum Ca²⁺ stores. Agonists were present at times shown by the horizontal bars. Dashed line shows the resting cytosolic [Ca²⁺]. (D) Bars indicate the change in cytosolic [Ca²⁺] from resting levels for myocytes that were store depleted in the absence (n=9) or presence of 8-Br-cAMP (n=6) or caffeine (n=10). Error bars represent ± S.E.M. Mean value significantly different from other groups by a One-Way ANOVA with a Newman-Keuls Multiple Comparison Test (P<0.05).