Effect of chronic vanadate ingestion on amino acid and water absorption in rat intestine.

Chronic administration of a relatively low concentration of vanadate to rats causes inhibition of water, alpha-aminoisobutyric acid (AIB) and L-alanine absorption. The mechanism responsible for this inhibition was tested by studying the uptake of alanine in isolated rat intestinal cells. The studies suggest that the vanadate inhibition of amino acid transport is primarily caused by a decreased activity of the Na+-K+ pump, an action that is similar to what is observed when the rat intestine is acutely exposed to vanadate. Vanadate appeared to have no direct effect on the entry of amino acids into the intestinal cell. This was evident by the fact that amino acid uptake by enterocytes of control rats was not different from the uptake by cells of vanadate-treated animals that have an inwardly directed Na gradient artificially created across them. Furthermore, 86RB influx and efflux into and out of intestinal tissues of the vanadate-treated animals were, respectively, decreased and increased as compared to normal control tissues and they were similar to what is observed when the intestine is acutely exposed to ouabain, a known specific inhibitor of the Na+-K+ pump.