MENON*, J.; MILITELLO, F. ; BUCHHOLZ, D. ; William Paterson University of New Jersey; William Paterson University of New Jersey; National Institute of Health: Oxidative stress during intestine remodeling in anuran tadpoles ,Xenopus laevis.

Development of many animals is associated with excessive production of reactive oxygen species (ROS) and/or decreased antioxidant capacity. Formation ROS is one of the factors underlying programmed cell death in tadpole tail � a larval organ – during anuran metamorphosis. Unlike the tail that regresses completely, intestine of tadpole undergoes extensive remodeling, where larval cells become apoptotic and larva to adult cells differentiate into adult intestine. We evaluated the role of oxidants (the levels of H₂O₂ and antioxidants (the activities of enzyme catalase – and reduced glutathione � GSH, a non-enzymatic antioxidant) in intestine during different developmental stages of tadpoles (Nieukoop and Faber (1967)) of Xenopus laevis. High levels of H₂O₂ observed in the present study during intestine remodeling (stage 60) could initiate cell death of the larval tissue, while simultaneous increase in catalase provides protection to larva – to – adult cells. Depletion in GSH content at this stage may trigger the activation of transcription factors required for apoptosis during intestine remodeling. Biochemical analysis and cytochemical observations on catalase in intestine shows high activity during stage 58, but not detected at stage 60-61. Our RT-PCR data indicate that in intestine, catalase is down regulated at stage 60, allowing free radicals to exert their full effects. Additionally, down regulation of catalase (RT-PCR) in thyroxine treated tadpoles would favor making the environment more pro-oxidizing. These data suggest that a decline in catalase and GSH precedes death of the larval cells in intestine and may contribute to an increase in cellular oxidative stress.