Figure 6.

Agonist-promoted internalization and down-regulation of β₂AR. (A) Cells were treated with the indicated agonists for 30 min at 37°C, and cell surface receptor was quantitated by hydrophilic radioligand binding with intact cells. *P < 0.01 versus Iso. (B) Cells were treated with the indicated agonists for 12 h at 37°C and solubilized, and proteins were subjected to 10% SDS-PAGE. Western blots were performed on the transferred proteins using a β₂AR antibody, and enhanced chemiluminescence and the immunoreactive bands were quantitated by a charged coupled device camera (see Materials and Methods). *P < 0.01 versus untreated but not different from each other. ^#P < 0.01 versus untreated and Iso, Form, and Fen but not different from each other.