Files in this Data Supplement:

• Figure I - (TIFF) (135 KB) Western blot analysis of protein expression of β₁, β₂, and M-2 receptors in control and HF hearts. There was no difference in the amount of receptor protein between controls or HF.
• Figure II - (TIFF) (32 KB) To test whether overnight culture had any significant effect on NCX activity or beta-adrenergic responsiveness, left ventricular myocytes were isolated from control and tachycardic pacing–induced failing swine hearts and cultured at 37°C in serum-free medium 199 supplemented with carnitine, creatine, taurine (as well as antibiotics). The Ni-sensitive NCX current (I_NCX) was measured both on the day of isolation (day-0) or after 24 hours culture (day-1) in both basal and isoproterenol-stimulated conditions. Overnight culture in serum-free medium did not change peak basal I_NCX or β-adrenergic responsiveness in either control or failing myocytes. HF significantly increased the basal I_NCX and reduced β-adrenergic responsiveness in both day-0 and day-1 cells (please see figure). We conclude that the NCX current and its responsiveness to β-adrenergic stimulation can be preserved in modified cell culture for 24 hours.