NHE2 AND NHE3 ARE HUMAN AND RABBIT INTESTINAL BRUSH-BORDER PROTEINS

Rabbit NHE2 and NHE3 are two epithelial isoform Na+/H+ exchangers (NHE ), the messages for which are found predominantly and entirely, respec tively, in renal, intestinal, and gastric mucosa. The current studies used Western analysis and immunohistochemistry to identify and charact erize the apical vs. basolateral membrane distribution of NHE2 and NHE 3 in intestinal epithelial cells. Based on Western analysis, NHE2 and NHE3 both are present in brush-border but not basolateral membranes of small intestine. Both NHE2 and NHE3 are 85-kDa proteins. Consistent w ith Western analysis, NHE2 and NHE3 are immunolocalized to the brush-b order but not basolateral membranes of villus epithelial cells, but no t goblet cells, in human jejunum and ileum and in surface epithelial c ells in the ascending and descending colon and rectum. In addition, NH E2 and NHE3 are present in small amounts in the crypt cell brush borde r of human jejunum, ileum, ascending and descending colon, and rectum. In rabbit jejunum, ileum, and ascending colon, NHE2 and NHE3 are pres ent in the brush border of epithelial and not goblet cells, again much more in the villus (small intestine)/surface cells (colon) than the c rypt. NHE2 but not NHE3 is present in the brush border of rabbit desce nding colon surface cells and in small amounts in crypt cells. NHE2 an d NHE3 are both human and rabbit small intestinal and colonic epitheli al cell brush-border Na+/H+ exchanger isoforms that colocalize in all intestinal segments except rabbit descending colon, which lacks NHE3.