Involved in vesicular storage and exocytosis of ATP. May accumulate ATP and other nucleotides in secretory vesicles such as adrenal chromaffin granules and synaptic vesicles (By similarity). In brain, specifically expressed in the medulla and is associated with chromaffin granules (at protein level). Predominantly expressed in adrenal gland, brain and thyroid. Belongs to the major facilitator superfamily. Sodium/anion cotransporter family.