Bicarbonate Secretion by the Rat Colon: Effect of Intraluminal Chloride and Acetazolamide 1

Summary

To examine the conditions under which bicarbonate is secreted by the colon, rats were perfused by a recirculation technique using solutions containing sodium and chloride, one or other of these ions, or neither. All solutions contained bicarbonate in concentrations greater than those in portal venous blood. In 12 animals, bicarbonate was secreted when chloride was a constitutent of the luminal contents, but bicarbonate was absorbed when chloride was excluded from perfusing solutions. Acetazolamide reduced the secretion of bicarbonate and the absorption of sodium, chloride, and water when sodium chloride solutions were used, but the drug had no effect on water and electrolyte transport when a chloride-free solution was used. These results suggest that carbonic anhydrase has a role in the exchange of bicarbonate and chloride across the mucosa of the colon and, further, they imply anion exchange may be related to the mechanism of sodium and water transport in the colon.