Plasma cortisol levels and expression of glucocorticoid receptors and oxidative stress markers in the fish Ombrina boccadoro exposed to transportation

Transportation of fish is a common practice among aquaculture facilities and it is known to cause stress influencing the release of catecholamines and corticosteroids as well as the expression of oxidative stress markers. It includes a complex of factors such as handling, air exposure, constraint and low oxygen levels that induce in fish an increase in metabolic rate, overexertion and in general a rapid deterioration of water quality. The aim of the work was to investigate muscle cortisol levels the expression of glucocorticoid receptors in liver and muscle and the cellular localization of HSP70, 8-OHdG, HNE and NT in several tissues of the teleost fish Ombrina boccadoro (Argyrosomus regius) exposed to transport stress. Fish transport has been carried out by a commercial truck and lasted 48 hours. Fish were sampled before and after loading and during and at the end of transport event (14 and 48 hours after departure). Muscle cortisol levels were investigated by a specific radioimmunoassay protocol, whereas the expression of glucocorticoid receptors was studied by Real Time PCR. Oxidative stress biomarkers were investigated by an immunohistochemical approach but no differences were detected between stressed and control animals. Both muscle cortisol and glucocorticoid receptor levels strongly increased after loading but decreased during transport indicating adequate transportation conditions. Aquaculture specialists will benefit from the present work by taking into consideration the importance of cortisol levels as well as of glucocorticoid receptor expression as stress indicators during transport and the importance of loading procedure to reduce stress during transport management.