Localization of amiloride-sensitive Na+ channels in intestinal epithelia

Polyclonal antibodies raised against purified bovine renal papillary amiloride-sensitive Na+ channels were used to localize Na(+)-channel proteins in mouse and piglet small intestine. Immunostaining using the avidin-biotin-peroxidase technique revealed epithelial Na(+)-channel epitopes localized to apical regions of villus enterocytes in jejunal tissues of both species. Anti-Na(+)-channel antibodies also stained apical borders of villus enterocytes in piglet ileum and apical borders of surface cells in the piglet distal colon. On immunoblots of jejunal, colonic, and renal tissues the anti-Na(+)-channel antibodies recognized one to three polypeptides of apparent molecular masses similar to those found in bovine renal epithelial Na(+)-channel protein (the 55-65, 110-116, and 150-kDa subunits). The antibodies also recognized a polypeptide in the 40- to 45-kDa range in mouse intestine, which is comparable to the 35- to 40-kDa subunit of a renal Na+ channel. The results demonstrate that epitopes comparable to those present in renal amiloride-sensitive Na+ channels are found in apical regions of absorptive epithelial cells in the mammalian small and large intestine.