Role of PKA in A2a receptor-mediated heterologous desensitization of RANTES receptors. (A) Effect of CGS21680 on cAMP accumulation in human monocytes. (B) Effect of a potent PKA inhibitor, cAMPs, Rp-isomer, TEA salt, at 100 μM (PKAI), on the inhibitory effects of CGS21680 (2 μM) on RANTES-induced chemotaxis. Effect of the potent PKA activator, N⁶-benzoyl-cAMP, at 1 and 10 μM (PKAA), on RANTES-induced chemotaxis in the absence of CGS21680. (C) Effects of PKAA at 1 μM on RANTES-induced Ca²⁺ influx. (D) Effects of a PKA inhibitor, cAMPs, Rp-isomer (PKAI), at 100 μM on CGS21680-induced inhibitory effects on RANTES-mediated Ca²⁺ influx. (E) Effects of a PKA inhibitor, cAMPs, Rp-isomer (PKAI), at 1 μM on CGS21680-induced inhibitory effects on MCP-1-mediated Ca²⁺-influx. ^*P < .001, by 2-way ANOVA analysis; ^**P < .03, by Student t analysis.