Electrogenic Sodium Bicarbonate Cotransporter 3 (NBC3)

The NBC3 cDNA, which lacks 3-prime coding sequence, encodes a deduced 670-amino acid partial polypeptide sharing 72% sequence identity with NBC2 and 53% identity with the kNBC variant of NBC1 (SLC4A4). Northern blot analysis of human tissues detected a 4.4-kb NBC3 transcript with high expression in brain and spinal cord, moderate expression in adrenal gland, lymph node, kidney, skeletal muscle, thyroid, and trachea, and low expression in liver, lung, placenta, pancreas, stomach, and bone marrow. In addition, 9- and 3-kb NBC3 transcripts were expressed in brain, spinal cord, and adrenal gland. In rat kidney, Nbc3 was expressed predominantly in the medulla. The authors demonstrated that subjecting cultured mouse inner medullary collecting duct cells to severe acid stress increased Nbc3 mRNA expression.