Sodium and chloride transport across the rumen epithelium of cattle in vitro: effect of short-chain fatty acids and amiloride.

Isolated mucosal sheets of cattle rumen were studied in vitro in Ussing chambers using a computer-controlled voltage clamp. Unidirectional fluxes of Na+ and Cl- were measured in standard (short-chain fatty acid (SCFA)-free) or SCFA-containing Ringer solution under zero voltage clamp conditions. Net NaCl absorption was observed under zero voltage clamp conditions, was stimulated by SCFAs and was not reduced by 1 mmol l-1 amiloride, although short-circuit current was significantly reduced by this concentration of the blocker. A constant coupling ratio of Na+ and Cl- absorption was observed.