Figure 5.

Stability of wild-type and CAM β₂-adrenergic receptor in Sf9 and myocardial particulate preparations. (A) Particulate fractions derived from Sf9 cells harboring either the wild-type or the CAM β₂-adrenergic receptor (10 pmol/mg and 2 pmol/mg, respectively) were prepared like myocardial samples (see Fig. 1). These preparations were incubated for various times at 37°C in ligand-binding buffer prior to the addition of radioligand (see Fig. 1). Shown is the average ± one-half of the difference of two experiments. (B) Myocardial particulate preparations of up-regulated CAM transgenic animals (≈10 pmol/mg) were incubated for 1 hr on ice (0°C) or at 37°C with no ligand (37°C) or in the presence of either 2 μM nadolol (nad), 100 nM alprenolol (alp), or 2 μM isoproterenol (iso). Membranes were pelleted and resuspended for 1 hr at 4°C in drug-free binding buffer, pelleted again, and assessed for binding as above. Shown are means ± SEM of 3–6 experiments.