Q. Once you isolate the cDNA for the receptor involved in mediating heart contraction, you sub-clone receptor cDNA into an expression plasmids and then stably transfect COS cells and choose the receptor-expressing COS-45 cell line. Using your receptor-expressing COS-45 cells, how could you demonstrate experimentally that the selective antagonist binds the receptor specifically? Illustrate the experiment you would perform and also the controls you would contain.