GPR41 is a GPCR that, along with GPR43, is activated by short chain carboxylic acids formate, acetate, proprionate, butyrate and pentanoate (Brown et al., 2003; Brown et al., 2005). Binding of these ligands to GPR41 selectively activates Gi to inhibit cAMP accumulation. Expression of GPR41 is prominent in adipose tissue, increases during differentiation of cultured adipocytes, and allows short chain carboxylic acids to stimulate leptin synthesis in adipocytes (Xiong et al., 2003). Millipore's GPR41 membrane preparations are crude membrane preparations made from our proprietary stable recombinant cell lines to ensure high-level of GPCR surface expression; thus, they are ideal HTS tools for screening of GPR41 interactions with its ligands. The cell line exhibits a calcium response with EC50s of 51.5μM for sodium propionate. The membrane preparations exhibit EC50s of 30.1 μM for sodium propionate in a GTPγS binding assay.