Acts as an electrogenic sodium (Na(+)) and chloride (Cl-)-dependent sodium-coupled solute transporter, including transport of monocarboxylates (short-chain fatty acids including L-lactate, D-lactate, pyruvate, acetate, propionate, valerate and butyrate), lactate, mocarboxylate drugs (nicotinate, benzoate, salicylate and 5-aminosalicylate) and ketone bodies (beta-D-hydroxybutyrate, acetoacetate and alpha-ketoisocaproate), with a Na(+):substrate stoichiometry of between 4:1 and 2:1. Catalyzes passive carrier mediated diffusion of iodide. Mediates iodide transport from the thyrocyte into the colloid lumen through the apical membrane (By similarity). In the gastrula and neurula stages, expressed in the gastrula anterior endoderm and in the entire circumference of the blastopore lip superficial endoderm. At tailbud stages, abundant expression observed in the ventral midgut region. As development proceeds expression becomes restricted to the liver diverticulum and ultimately to the presumptive gallbladder, by tadpole stage 35. Also present in pronephros and the tip of the tail. Belongs to the sodium:solute symporter (SSF) (TC 2.A.21) family.