Fig. 9.

Chronic pretreatment of the human airway smooth muscle strips with propionate did not potentiate isoproterenol-induced relaxation. A: representative tension tracings in human airway smooth muscle strips after an acetylcholine (EC₅₀) concentration followed by increasing concentrations (0.1 nM–10 µM) of the β-adrenoceptor agonist isoproterenol in the presence or absence of propionate (60 min pretreatment; 10 mM), illustrating that isoproterenol-induced relaxation of ACh (EC₅₀) contraction was not potentiated by chronic pretreatment with propionate (10 mM) indicating an absence of adenylyl cyclase sensitization by chronic propionate activation of G_i. B: isoproterenol concentration response relaxation curves in the presence or absence of propionate (60 min pretreatment; 10 mM). Data represent means ± SE; n = 6. C: EC₅₀ value of isoproterenol-induced relaxation with or without propionate pretreatment (60 min pretreatment; 10 mM). Data represent means ± SE; n = 6.