Figure 7. Functional analysis of GPR109A expression in ARPE-19 cells. ARPE-19 cells were treated in the presence or absence of 10 μM forskolin,1 mM nicotinic acid, or 1 mM β-hydroxybutyrate (β-HB) for 1 h followed by measurement of intracellular cAMP levels. Cells incubated in the presence of forskolin alone showed a large increase in intracellular levels of cAMP. This increase was reduced by the addition of nicotinic acid or β-HB to the culture medium, indicating activation of GPR109A. Data are mean±SEM from three separate experiments.