(A) Saturation isotherm of [3H]MRS 1754 binding to human A2B receptors expressed in HEK-293 cell membranes, and (B) Scatchard analysis of the same data. [3H]MRS 1754 (0.1 to 20 nM) was incubated with 30 μg of membranes for 60 min at 25°. Total binding (○), specific binding (●), and nonspecific binding (Δ), determined using 100 μM NECA, are shown in (A). Four experiments were carried out; data from one representative experiment are shown.