An in vitro assay useful to determine the potency of several bitter compounds

Gustducin and transducin are guanine nucleotide binding regulatory proteins (G proteins) expressed in taste receptor cells and implicated in transduci ng taste cell responses to certain compounds that humans consider bitter or sweet. These G proteins can be activated in vitro by taste receptor-contai ning membranes plus any of several bitter compounds. This activation can be monitored using limited trypsin digestion, sodium dodecylsulfate-polyacryl amide gel electrophoresis (SDS-PAGE) and immunoblotting. Scanning of the au toradiograms enables one to quantitate the level of activation (defined as an activation index), obtain dose-response profiles and estimate the potenc y of the tastant. This assay may provide a useful substitute for, or adjunc t to, the time-consuming human psychophysical analysis and costly animal st udies typically used in taste sensory analysis. it may be used to identify and determine the concentration-response function of many bitter components of oral pharmaceuticals and food ingredients. A potential limitation of th e assay is that only about half of all bitter compounds tested demonstrated in vitro activity, perhaps due to the presence of multiple transduction pa thways. Nevertheless, the rapid throughput and microsample handling capabil ity of this assay make it an ideal method to screen for high-potency bitter ness inhibitors.