TABLE 2
Nicotinic acid and acifran evoked Ca2+ responses (EC50) and nicotinic acid binding affinity (Kd) for aromatic residue mutants of GPR109A Shown are data for the indicated GPR109A mutants. The EC50 values of nicotinic acid-induced increases in [Ca2+]i were determined in CHO-K1 cells expressing Gα15 and the indicated wild-type or mutant receptors. The KD and Bmax values were determined by Scatchard analysis of [3H]nicotinic acid binding saturation isotherms and represent the mean ± S.D. of at least three independent experiments. Relative cell surface expression levels of wild-type and GPR109A receptor mutants were determined by ELISA assay in nonpermeabilized CHO-K1 cells (see Materials and Methods).