Comparative assessment of the antioxidative defense system in subadult and adult anurans: A lesson from the Bufotes viridis toad

During their complex life cycle, anurans are faced with various physiological and biochemical demands that can result in increased free radical production. The antioxidative system (AOS), assumes a central role in protection from oxidative stress, and increased knowledge of its response would allow us to identify and quantify underlying costs of free radical production. In this study, we compared the patterns and levels of integration of the AOS during two life stages of Bufotes viridis toads from natural populations: young, fully developed, reproductively inactive subadults and reproductively active adults. All examined parameters (SOD, CAT, GSH-Px, GR, GST, GSH and SH groups) were measured in the liver, skin and muscle. The obtained results showed that: (1) subadult individuals possessed a more integrated AOS (a higher index of integration and number of significant correlations), based mostly on the coordinated action of SOD-CAT; (2) adult individuals used the GSH-Px/GSH system; (3) all examined tissues exhibited similar patterns of variation of AOS parameters; (4) significant correlations between the AOS and biometric parameters. Our results indicate that adult and subadult toads differed in the way they processed free radicals, implying that adults may be more susceptible to oxidative damage. The knowledge from this study will contribute to a better understanding of the AOS and how its activity is modulated in natural populations of anurans throughout their life.