Twenty-one patients (age 58 ± 7 years, 13 men) with AF were randomly assigned to either 75, 150, or 300 μg intravenous tecadenoson. Tecadenoson was administered alone (Dose Period 1) and in combination (Dose Period 2) with esmolol (100 μg/kg/min for 10 min then 50 μg/kg/min for 50 min).

Transport of [3H]tecadenoson was assessed at room temperature (RT) with a high-throughput assay. Yeast were grown in CMM/GLU to an optical density (OD)600 of 0.8–1.2, washed three times with fresh CMM/GLU (pH 7.4), and re-suspended to an OD600 of 4 in CMM/GLU (pH 7.4). For tecadenoson transportability assays, uptake of 1 mM [3H]tecadenoson was measured alone or with 10 mM nonradioactive uridine. The transport assays were initiated by adding an equal volume of yeast suspension at OD600 = 4 to each of the individual wells of the preloaded 96-well plates, which were placed on the semi-automated cell harvester. At graded time intervals, groups of transport reactions (usually 24) were terminated simultaneously by harvesting yeast on glass-fiber filters (Skatron Instruments) with continued washing with demineralized water to remove unincorporated permeant. The filter discs with yeast corresponding to a particular transport assay were placed into individual scintillation counting vials (1 disc/vial) to which 5 ml scintillation counting fluid (EcoLite; ICN Biomedical Inc., Aurora, OH) was added. Scintillation vials were allowed to sit at RT overnight with shaking before analysis.