The response of thyroid hormones, biochemical and enzymological biomarkers to pyrene exposure in common carp (Cyprinus carpio)

•Pyrene disturbed normal functioning of thyroid system and reduced plasma T3 and T4.•Aminotransferases (ALT, AST and ALP) markedly changed after exposure to pyrene.•Pyrene did not significantly changed plasma sodium, potassium and calcium levels.

Polycyclic Aromatic Hydrocarbons (PAHs) are discharged into aquatic environments through anthropogenic activities mainly industrial and municipal effluents. There is little information on the adverse effects of pyrene, a member of the PAH family which is classified as a priority pollutant by the USEPA, on fish biochemical and physiological endpoints, particularly thyroid hormones. The present study investigated the effects of subacute semi-static pyrene exposure on biochemical, enzymological and ionoregulatory responses as well as thyroid hormones in common carp (Cyprinus carpio). The fish (140±10 g, 1+ year) were exposed to 10, 50 and 100 µg/l nominal concentrations of pyrene for 35 days. The results revealed that pyrene at these concentrations significantly altered plasma levels of glucose, cholesterol, triglyceride, total protein, albumin, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP). Moreover, plasma thyroid hormones (T3 and T4) were significantly decreased in fish exposed to pyrene. In contrast, plasma electrolytes (sodium, potassium and calcium) levels remained statistically unchanged after exposure to the various pyrene concentrations. In conclusion, the studied biomarkers may be used as monitoring tools to evaluate pyrene toxicity. Pyrene induced diverse effects on the physiological endpoints of common carp, thus this chemical should be considered in toxicity studies concerning PAHs. Furthermore, this study confirmed that there was an interaction between pyrene and the thyroid system in fish. Therefore, the thyroid system may be used to assess the impact of pyrene on fish.