FIGURE 7.

Adenosine reduces forskolin-evoked cAMP rise in cultured cells expressing Adora3i2. tsA-201 cells expressing cloned mouse Adora3i2 tagged with RFP (Adora3i2) or expressing cytosolic GFP alone (Mock) were treated with medium that was supplemented at (t = 0) with either: no additions (None), 30 μm Cl-dAdo, 3 μm forskolin (FSK), or with 3 μm forskolin after addition of 30 μm Cl-dAdo at t = −5 min (Cl-dAdo + FSK). At t = 15 min, assays were terminated and cAMP content of the neutralized extracts was determined by radioimmunoassay. Protein content was determined on assay of parallel cultures. The right axis shows responses normalized to the mean basal content and the mean content of cells treated with forskolin alone. The cAMP content of Adora3i2-expressing cells was reduced significantly (∼60%) for cells receiving Cl-dAdo prior to addition of forskolin compared with cells challenged with forskolin alone. Double asterisk indicates p < 0.002.