ClC-2 in guinea pig colon: mRNA, immunolabeling, and functional evidence for surface epithelium localization
The principal function of the colon in fluid homeostasis is the absorption of NaCl and water. Apical membrane Na+ channels, Na+/H+ and Cl-/HCO3- exchangers, have all been postulated to mediate NaCl entry into colonocytes. The identity of the basolateral exit pathway for Cl- is unknown. We have previously demonstrated the presence of the ClC-2 transcript in the guinea pig intestine. Now we explore in more detail, the tissue and cellular distribution of chloride channel ClC-2 in the distal colon by in situ hybridization and immunohistochemistry. The patch-clamp technique was used to characterize Cl-currents in isolated surface epithelial cells from guinea pig distal colon and these were compared with those mediated by recombinant guinea pig (gp)ClC-2. ClC-2 mRNA and protein were found in the surface epithelium of the distal colon. Immunolocalization revealed that, in addition to some intracellular labeling, ClC-2 was present in the basolateral membranes but absent from the apical pole of colonocytes. Isolated surface epithelial cells exhibited hyperpolarization activated chloride currents showing a Cl- > I- permeability and Cd2+ sensitivity. These characteristics, as well as some details of the kinetics of activation and deactivation, were very similar to those of recombinant gpClC-2 measured in parallel experiments. The presence of active ClC-2 type currents in surface colonic epithelium, coupled to a basolateral location for ClC-2 in the distal colon, suggests a role for ClC-2 channel in mediating basolateral membrane exit of Cl- as an essential step in a NaCl absorption process.
|Título según WOS:||ClC-2 in guinea pig colon: mRNA, immunolabeling, and functional evidence for surface epithelium localization|
|Título según SCOPUS:||ClC-2 in guinea pig colon: mRNA, immunolabeling, and functional evidence for surface epithelium localization|
|Título de la Revista:||AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY|
|Editorial:||AMER PHYSIOLOGICAL SOC|
|Fecha de publicación:||2002|
|Página de inicio:||G1004|