Endocrine Abstracts

Potassium-dependent sodium/calcium exchanger (NCKX3) is expressed in the brain, smooth muscle, the uterus, and intestine. NCKX3 gene plays a role in transporting intracellular calcium and potassium ions across the cell membrane in exchange for extracellular sodium ions. This gene is also associated with calcium metabolism in bones. Tight junctions have functional barriers for material transport and osmotic balance, which are regulated by calcium metabolism. Claudin, one of the tight junction protein members, take a part in a barrier preventing free diffusion and generate the paracellular pore pathway with unique cation- or anion-selectivity. The study has investigated the expressions of intestinal epithelial claudin genes in the duodenum of 6 week-aged Nckx3 knockout (KO) mice. The mRNA and protein levels of claudin-2, 5, and -15 were increased in Nckx3 KO mice compared to wild-type mice. However, mRNA and protein levels of claudin-12 were decreased in Nckx3 KO mice. We also found that Ifit1, Zbp1, Oasl1, Oasl2, H2-DMb1 and H2-Aa genes were up-regulated in Ncxk3 KO mice, and Gkn2, Gkn3, Tff2 and Tff1 genes were down-regulated in Ncxk3 KO mice in gene expression profiles using an Affymetrix GeneChips. These results suggest that the NCKX3 gene may be involved in tight junction and calcium metabolism in duodenum.