Mechanisms of sodium and chloride transport across isolated sheep reticulum

Abstract

1. 1. 22Na + and 36Cl − fluxes across isolated reticular epithelium of sheep were measured by using the Ussing-chamber technique. 2. 2. Net NaC1 absorption driven by Na +-K +-ATPase was observed under short-circuit conditions. 3. 3. Evaluation of fluxes measured under voltage-clamp conditions indicated that Na + absorption is mainly electroneutral. 4. 4. Mucosal application of bumetanide, hydrochlorothiazide, or low dose amiloride (10 − 4 M) produced no changes in Na + transport whereas addition of higher doses of amiloride (⩾10 −3 M) led to a reduction in net Na + transport. Short chain fatty acids (SCFA) enhanced the amiloride-sensitive Na + transport. 5. 5. Alterations of J ms na induced by inhibitors or by SCFA were always accompanied by qualitatively similar changes of J sm na. Amiloride-sensitive J sm na was also decreased at low mucosal Na + concentration. 6. 6. DIDS, SITS, and nitrate reduced both J ms cl and J sm cl. SCFA did not influence chloride transport. 7. 7. It is concluded that Na + transport is mediated by Na +-H + exchange and by transport processes operating as Na + self-exchange. Mucosal-to-serosal chloride transport seems partly to depend on anion exchange systems.