Oxidative damages and antioxidant defences after feeding a single meal in rainbow trout

Feeding and digestion are metabolically demanding causing a rise on metabolic rate called Specific Dynamic Action (SDA). Although SDA has been vastly reported in fish, its potential consequences on the oxidative-antioxidant balance has not been evaluated to date in fish, a model with a long alkaline tide associated with feeding as well. Using rainbow trout (Oncorhynchus mykiss) as a model species, the aims of the present study were to: (1) assess potential oxidative damages and changes in oxidative defences after feeding on a single meal, and (2) identify the timescale of such changes over a 96 h post-feeding period. Oxidative damage in proteins and lipids and the activities of four enzymatic antioxidant defences: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) were measured in gill, stomach, intestine and liver. DNA damage was measured in red blood cells. Fish were sampled before and after 1.5, 6, 24, 48, 72 and 96 h of ingestion of a 3% body mass ration. Trends of post-prandial damage were present in all tissues, but only protein oxidation varied significatively during digestion in the stomach. The intestine and stomach presented the highest enzymatic activities, likely due to the high metabolic action that these tissues have during digestion, with peaks during post-feeding: at 24 h of SOD in stomach and at 48 h of CAT in intestine. Observed GPx peaks during post-feeding in gills are likely due to the exacerbated demands for ion fluxes and/or oxygen during feeding. The differential response of the antioxidant system observed in tissues of rainbow trout during digestion indicates a coordinated and tissue-specific antioxidant defence.