Fig. 5.

β-adrenoceptor agonist activates the adenylate cyclase pathway and initiates increased intracellular Ca²⁺ and NO release in rat urothelial cells.A, Inset, Transient NO release from urothelial cells elicited by application of isoproterenol (ISO; [Ca²⁺]_o = 1.8 mm) was diminished in the absence ([Ca²⁺]_o ≈ 0) of extracellular calcium (100 μm EGTA). The graph depicts isoproterenol-elicited NO production in urothelial cells (percentage change in NO): [Ca²⁺]_o ≈ 0; isoproterenol-evoked NO release is diminished in the absence of extracellular Ca²⁺. NIF, Reduction of isoproterenol-evoked NO release after incubation with the L-type Ca²⁺ channel antagonist nifedipine (10 μm); BAYK, increase in isoproterenol-evoked NO release after incubation with BAYK8644 (10 μm); Caffeine, significant reduction in isoproterenol-evoked NO release after repeated (n = 3) incubations with caffeine (10 mm);BAPTA-AM, block of transient isoproterenol-evoked NO release after incubation with BAPTA-AM (5 μm). A similar response was detected in bladder strips (data not shown).B, Transient NO release elicited by increasing concentrations (10–100 μm) of the membrane-permeant cAMP analog dibutyryl-cAMP. Arrows indicate the start of drug application, which occurred 3 sec before the onset of NO release.C, Isoproterenol-evoked NO release from isolated urothelial cells is enhanced (percentage change in NO) after incubation with either forskolin (10 μm) or the phosphodiesterase inhibitor IBMX (50 μm). Data are based on calculations from 30 to 50 cells per treatment, recorded in a minimum of three independent experiments. Values represent mean ± SEM; *significantly different from isoproterenol alone.