Abstract: AIM: To set uPthe screening model for glucagon receptor(GR) antagonist.METHODS: Rat liver glucagon receptor was prepared by centrifugation.The binding characteristics of GR ligand (¹²⁵I-Glucagon) were studied by radioligands binding in saturation binding experiments and followed by competition binding experiments with a variety of new synthesized compounds.In order to further study the method for screening GR antagonists,GR cDNA was transiently transfected into CHO cells, and then fluo-3 was loaded into the cells.The most important properties of fluo-3 are an absorption spectrum compatible with excitation at 506 nm by argon-ion laser sources and very large fluorescence intensity increase in response to Ca²⁺binding.In the studies, transfected CHO cells were loaded with both fluo-3 and compounds,and then fluorescence intensity was measured to identify GR antagonists.RESULTS: The Kd and Bmax of¹²⁵IGlucagon to GR were 9.38 nmol·L^-1 and 4.33nmol·L^-1 , respectively.Competition binding experiments revealed that compounds ZM102849, ZM102850,ZM102854 and ZM102855 displayed much higher affinity for the GR.When compound ZM102850 was added to the transfected cells, the fluorescence intensity decreased.Therefore, compound ZM102850 was identified as a glucagons antagonist.CONCLUSION: Combining radioimmunoassay and measuring the fluorescence intensity methods can be used to identify GR antagonists.

Key words: radioimmunoassay, glucagon receptor, 125 I-Glucagon, antagonist, CHO cell, transfection