Endocrine responses during acute and chronic Benzo-α-Pyren (BaP) exposure stress in Yellowfin Seabream, Acanthopagrus latus

The present study carried out to assess the effects of Benzo-α-Pyren (BaP), as an important Polycyclic Aromatic Hydrocarbon (PAH) on the plasma levels of cortisol and triiodothyronine (T3) hormones in male Seabream, Acanthopagrus latus (Sparidea). To assess the acute effects of BaP on the endocrine system, a group of fish was injected with dissolved BaP in sunflower oil (50mg/kg BaP in 2μg/l oil according to the body weight). Other fishes were injected with 2μg/l body weight as controls. Blood samples from both groups were collected 3 hours after injection. In another protocol, the chronic effects of BaP on the plasma levels of cortisol and T3 were assessed. Another group of fish was implanted with 50mg/kg BaP in 10μl/g coconut oil in respect to fish body weight. A control group was implanted with the same amount of oil without the BaP. Blood samples were collected from both implanted groups (treatment and control) after 72 hours. Plasma levels of cortisol in yellowfin Seabream increased during both short time and long time exposure but T3 levels in the plasma decreased during the chronic stress of BaP exposure. It seems that the cortisol levels are elevated to meet the increased energy requirement under the acute and chronic stress conditions by direct effect on glyconeogenesis and fast blood sugar level to be consumed by cells. T3 levels may be affected by inhibitory effect of Aryl hydrocarbon receptors (AhRs) which decreased it during long term exposure.