Glutathione and GSH-dependent enzymes in the gastrointestinal mucosa of the rat.

The mucosal glutathione content of the gastrointestinal wall amounted to 50-60% of its concentration in the liver. GSH S-aryltransferase activity (CDNB) was very low in the glandular stomach, colon and rectum amounting to only 5% of liver enzyme activity. There was a marked postpyloric increase in GSH S-aryltransferase activity with an oral-aboral decline along the small intestine. GSH peroxidase was much lower in the mucosa of the small and large intestine as compared to the stomach or liver, whereas GSSG reductase was more than twice as high in the gastrointestinal mucosa as compared to the liver showing a gradual increase in activity from proximal to distal segments. The low GSH S-transferase activities found in the stomach, colon and rectum may account for the high and exclusive susceptibility of these segments to carcinogenesis and the deficient inducibility of these enzymes in the gastrointestinal wall may reflect an insufficient adaption towards higher exposure to toxic or even carcinogenic xenobiotics.