Season Dependent Response of the Marsh Frog (Rana ridibunda) to Cadmium Exposure

Cadmium toxicity related to cysteine metabolism and glutathione levels in several tissues of the Marsh frog (Rana ridibunda) collected in late spring were investigated after exposure to 80 mg CdCl₂ L⁻¹ for 168 h. The results were compared to those obtained in a previous experiment carried out in autumn. The most striking changes involved the brain which could not maintain a proper glutathione level and the testes in which neither GSH nor sulfane sulfur levels recovered. Substantial damage is expected in the presence of Cd which decreases the antioxidant status of these tissues. It seems that in spring, frogs had lesser tolerance for Cd in comparison with frogs in autumn. This may be caused by the transition to aerobic respiration after hibernation.