Fig. 8.

³H-cAMP accumulation in response to CGP12177 (A and C) and pindolol (B and D) in transiently transfected cells expressing β₁-V189T-L195Q-W199Y (A and B) and β₁-W199D (C and D). The CGP12177 responses were examined in the absence and presence of 3, 10, and 30 nM cimaterol. Bars represent basal ³H-cAMP accumulation, that in response to 10 µM isoprenaline or that in response to 3, 10, and 30 nM cimaterol alone. Data points are mean ± S.E.M. of triplicate determinations. These single experiments are representative of (A) three, (B) four, (C) six, and (D) four separate experiments. This figure shows that the “dip” in the CGP12177 + cimaterol curve and biphasic pindolol response, both present at β₁-WT with two conformations (see Fig. 6A), are absent in β₁-V189T-L195Q-W199Y and β₁-W199D, suggesting that neither of these receptors has the secondary conformation.