The SLC4A4 gene encodes the Na+-HCO3? co-transporter (NBC), which is involved in the regulation of bicarbonate secretion and absorption and intracellular pH. There is the kidney-type transporter (kNBC1) and the pancreatic-type transporter (pNBC1). kNBC1 plays an important role in bicarbonate absorption from renal proximal tubules, whilst pNBC1 is involved in bicarbonate secretion from pancreatic duct cells.
SLC4A4 is also widely expressed in several ocular tissues, such as the corneal endothelium, trabecular meshwork, pigmented and nonpigmented ciliary epithelium, and lens epithelium. Three transcripts are encoded by the SLC4A4 gene.