Cloning and Expression of Sodium-Bicarbonate Cotransporter Isoform in Rat / 대한해부학회지

ABSTRACT

The potassium depletion has remarkable and opposite effect on kidney and body growth and has affected the expression of the several ion transporters. Previously, Ahn et al. have reported that HK alpha 1 and 2 subunit gene were upregulated in the hypokalemic rat kidney. To clone the unreported genes expressed in potassium deficiency, differential display PCR-based cloning strategy was used in normal and potassium-depleted rat kidney and a novel gene was isolated. Sequence analysis with blast search program identified a cDNA clone encoding an isoform of kidney sodium bicarbonate cotransporter-1. The tissue and cellular expression pattern of this gene were investigated with Northern analyses and in situ hybridization histochemistry (ISH) in normal and hypokalemic rats. This novel transcript was highly expressed in kidney and brain and at lower levels in distal colon, urinary bladder, and heart but not in salivary gland, stomach, liver, and lung in normal rat. In potassium-depleted rat, this transcript was upregulated in kidney, brain, and distal colon. By ISH, cellular distribution of this gene was highly expressed in S3 segment of proximal tubule, distal convoluted tubule, and cortical collecting duct of kidney and lower third of intestinal glands of distal colon but at lower levels in cortical and medullary thick ascending limb and medullary collecting duct of kidney and middle third of intestinal glands of distal colon. From these results, this candidate gene may play an important role in HCO3-transport by these organs during potassium depletion.