D-Phenyllactic acid is a potent agonist acting at HCA₃.

(A) CHO-K1 cells were transiently transfected with human HCA1, HCA2, HCA3, and empty vector (control), seeded in fibronectin-coated Epic plates and DMR responses were recorded upon stimulation with 1 μM D-phenyllactic acid (D-PLA), 100 μM L-phenyllactic acid (L-PLA) and 1 μM indole lactic acid (ILA) to reveal potential differences in receptor activation kinetics. Shown is the agonist-induced shift in pm of three independent experiments carried out in triplicates. (B) The agonist-induced inhibition of forskolin-induced cAMP accumulation was determined in CHO-K1 cells transiently transfected with HCA3 orthologs and empty vector. Concentration-response curves upon stimulation with D-PLA, L-PLA and ILA are depicted as fold over over forskolin-stimulated cAMP level in the absence of agonist of each ortholog. Data is given as mean ± SEM of at least three independent experiments each carried out in triplicates. A general explanation of EC50 values is provided in the results section Functional hominoid HCAR analyses with known endogenous agonists. (C) log EC50 values (corresponding to EC50 values shown in Table 3) are plotted as mean ± 95% confidence interval. Statistical analyses were performed using an ordinary One-Way ANOVA (Dunnett’s multiple comparisons test) testing against orang utan HCA3. # ≤ 0.1, * P ≤ 0.05; ** P ≤ 0.01; *** P ≤ 0.001.