THE EXPRESSION OF AN INTESTINAL FORM OF GLUTATHIONE-PEROXIDASE (GSHPX-GI) IN RAT INTESTINAL EPITHELIUM

We have previously identified and characterized GSHPx-GI, which is a c ellular selenium-dependent glutathione peroxidase (GSHPx) distinct fro m the classic GSHPx-1 and phospholipid hydroperoxide glutathione perox idase (PHGPX). We have determined the level of GSHPx-GI mRNA expressio n in the rat gastrointestinal tract from esophagus to colon. Although GSHPx-GI mRNA is readily detectable throughout the GI tract, the highe st level is detected in the ileum and cecum. We have also determined t he levels of GSHPx-GI mRNA expression and several antioxidant enzyme a ctivities along the villus-to-crypt axis in the rat small intestine by cell fractionation. GSHPx-GI mRNA is present at a similar level in al l of the epithelial fractions, whereas GSHPx-1 mRNA is detectable only in the remnant. This suggests that GSHPx-GI is the major cellular tet rameric GSHPx expressed in intestinal epithelium, and the expression o f GSHPx-GI in the GI tract is not likely regulated differentially thro ugh maturation of epithelial cells. In terms of enzymatic activity, al though we detected lower glutathione S-transferase activity in the cry pt epithelium, there was a marginal increase of PHGPX activity, a twof old increase of GSHPx activity, and a three- to fivefold increase of c atalase activity in the crypt relative to the distal villus. Thus, the crypt epithelial cells may be better protected from peroxidative dama ge. (C) 1995 Academic Press, Inc.