Hyperoxia decreases lung size of amphibian tadpoles without changing GSH-peroxidases or tissue peroxidation.

1. During the development of D. pictus larvae (Amphibia) in normoxia, selenium (Se) GSH-Px increased whereas non-Se GSH-Px did not change. 2. Acclimation to 60 or 100% O2 did not change Se GSH-Px or non-Se GSH-Px. 3. Hyperoxia did not change tissue peroxidation (TBA-RS) confirming the good capacity of D. pictus tadpoles for O2-adaptation. 4. Since hyperoxic induction of catalase (CAT) has been previously described in D. pictus tadpoles, it is concluded that CAT is more important than both GSH-Px for the establishment of O2-adaptation. 5. Increases of Se GSH-Px, SOD and CAT, are probably important for adaptation to the change from aquatic to aerial environment during metamorphosis in normoxia. 6. Chronic exposure to 100% O2 enormously reduced the lung size of D. pictus larvae.