The preparation, solubilisation and binding characteristics of a beta 2-adrenoceptor isolated from transfected Chinese hamster cells

beta2-Adrenoceptor agonists (beta -agonists) are well known for their growt h promoting and repartitioning effects in many species. Although the use of these compounds to increase muscle mass in stockfarming is prohibited with in the EU, under directive 96/22/EC, significant illegal use still occurs. With legal and illegal synthesis of new structurally related compounds, the detection of traditional beta -agonists and new derivatives becomes increa singly problematical. This method describes the isolation and solubilisatio n of a beta2-adrenoceptor from a transfected Chinese hamster ovary cell lin e, using the detergent digitonin. The solubilised receptor retained its act ivity and was isolated from the cell membrane at a concentration of 550 +/- 100 fmol mg(-1) of solubilised protein. Competition analysis using the tri tiated antagonist dihydroalprenolol revealed receptor affinity for five str ucturally different beta -agonists, with IC50 values ranging from 2.1 +/- 0 .76 X 10(-7) M for salmeterol to 1.1 +/- 0.62 x 10(-5) M for ractopamine. T his study has demonstrated that transfected cell lines with a high expressi on of beta2-adrenoceptors are a convenient source of active receptor materi al. Solubilised beta (2)-adrenoceptors could form the basis of a multi-anal yte screening assay for use in routine screening.