FLIPR® membrane potential dye measures changes of charges across the cell membrane, upon activation of SLC13A3. The assay allows the detection of ion channel and transporter modulation by increasing or decreasing the fluorescent signal as cellular membrane potential changes. When cells are depolarized dye enters the cells, causing an increase in fluorescent signal, conversely, cells hyperpolarization results in dye exit and decreased fluorescence. SLC13A3 is the human Na+/dicarboxylate cotransporter that couples 3 Na+ ions to the transport of each divalent anion substrate. It transports a broad range of substrates including dicarboxylates containing from four to six carbon atoms (e.g., succinate), as well as tricarboxylates (e.g., citrate). It is an electrogenic transporter eligible to be studied using the membrane potential dye.