Impairment of the stress response in matrinxã juveniles (Brycon amazonicus) exposed to low concentrations of phenol

In this study we measured plasma cortisol, plasma glucose, plasma sodium and potassium, and liver and gill hsp70 levels in juvenile matrinxã (Brycon amazonicus) subjected to a 96 h exposure to phenol (0, 0.2, and 2.0 ppm), and the effect of this exposure on their ability to respond to a subsequent handling stress. Fish were sampled prior to initiation of exposure and 96 h, and at 1, 6, 12, and 24 h post-handling stress. During the 96 h exposure, plasma cortisol and glucose levels remained unchanged in all treatments. While plasma sodium levels were significantly reduced in all groups, plasma potassium levels only decreased in fish exposed to 0 and 0.2 ppm of phenol. Liver hsp70 levels decreased significantly at 96 h in fish exposed to 2.0 ppm of phenol. All groups, except fish exposed to 0.2 ppm of phenol, were able to increase plasma cortisol and glucose levels after handling stress. Fish exposed to 2.0 ppm of phenol showed decreased gill and liver hsp70 levels after the handling stress. Our data suggest that exposure to phenol may compromise the ability of matrinxã to elicit physiological responses to a subsequent stressor.