MENON*, JAISHRI; GRESKO, DARCI; GARDNER, EILEEN; William Paterson University of New Jersey, Wayne, NJ: Role of Peroxisomal Enzymes and Peroxisome Proiliferator Activated Receptors (PPAR) in Intestine Remodeling of Anuran tadpoles, Xenopus laevis

Programmed cell death plays a major role in the transformation of larval intestine into adult type. One of the mechanisms leading to cell death is via production of reactive oxygen species (ROS) such as superoxide radical anion, hydrogen peroxide (H₂O₂) and lipid peroxides. In the present study, tissue localization of D-amino oxidase (DAOX), urate oxidase (UOX) (both of which produce H₂O₂) and catalase (which breaks down H₂O₂) was carried out in intestine of X. laevis tadpoles using cerium-DAB visualization (for DAOX and UOX) and DAB (for catalase). Additionally, quantitative changes in catalase enzyme, H₂O₂ productions as well as western blot analysis for PPAR were evaluated. Tadpoles were staged according to Nieukoop and Faber (1967). Our findings show presence of catalase and DAOX in intestine at stage 61/62 � a time period that coincides with its remodeling. Both the enzymes showed a discrete granular distribution compatible with peroxisomal compartmentalization. However, catalase activity was only noted in the mucosa of the intestine fated to give rise to adult mucosa but not in the typhlosole of the intestine (a larval structure), which degenerates fully during its remodeling. No UOX was noticed at any stage of metamorphosis. These observations suggest that at the time of intestine remodeling a) The cellular environment becomes more pro-oxidizing, which might be responsible for the cell death and differentiation. b) Catalase activity during the same period would minimize cellular oxidative stress by lowering concentration of H₂O₂. C) Evidence of PPAR expression in the intestine correlates with higher peroxisomal enzyme activity.