Figure 1.

β-AR signaling defects in ventricular myocytes isolated from chronically paced rabbit hearts. (A) β-AR density was determined from myocardial sarcolemmal membranes prepared from ventricular myocytes isolated from control (sham-operated) or CHF (paced) rabbits (n = 5 in each group; ∗, P < 0.05 vs. control). (B) Basal and ISO-stimulated intracellular adenylyl cyclase activity was determined for control (open bars) and CHF ventricular myocytes (filled bars) (n = 5 myocyte preparations each; ∗ P < 0.05 vs. control). (C) Levels of expression of βARK1 in whole-cell extracts were assessed by protein immunoblotting. Shown is the average data for five myocyte preparations isolated from control (sham) and CHF (paced) rabbit hearts. βARK1 densitometry values from control immunoblots were arbitrarily set to 1 and all values were normalized to controls. The Inset shows a representative protein immunoblot from two control and two CHF preparations with purified βARK1 used as a marker (∗, P < 0.05 vs. control).