Use of tissue chromogranin A as chronic and acute stress marker in fish

Abstract

Chromogranin A (CgA) has recently reported as stress marker in superior vertebrates. It is stored in granules of the chromaffin tissue and released to the bloodstream from the adrenal medulla and pituitary after stress situations. The objective of this work was to study the chromogranin A variation for acute and chronic stress in fish, aiming at determining if those proteins could be suitable stress markers. A chronic stress experiment was conducted consisting of two treatments, stressed and control meagres (Argyrosomus regius) for 6 months. The stressed groups were submitted to confinement and netting/chasing stress. The control group tanks were not disturbed along the experiment. A complementary acute stress challenge was performed exposing control fish to air for 3 min. Fish were sampled for blood, tissues and biometry. Plasma lactate and cortisol increased significantly after acute stress although glucose and proteins remained stable, and kidney cortisol and brain adrenaline were significantly higher. Kidney CgA decreased significantly in the acute stressed fish though brain CgA did not change. Final weight and length, growth and condition index were significantly lower in chronically stressed fish, though survival rate was not different between treatments. Plasma markers did not change significantly though kidney cortisol increased in chronically stressed fish. Brain noradrenaline was lower in chronically stressed fish. Both brain and kidney CgA concentrations decreased in stressed (chronic and acute) fish. Concluding, only kidney CgA and cortisol kept the same variation pattern in both stress types. Although cortisol concentrations in plasma and tissues have been widely studied, the tissue CgA concentrations related to stress have not still reported in fish. Initially, the depletion of kidney CgA could be considered as a chronic stress marker though it needs to be supported by future research.