A STUDY OF THE EXPRESSION OF CYP1A IN SPARUS AURATA GILLS AND LIVER FOLLOWING EXPOSURE TO BENZO[A]PYRENE

Cytochrome P4501A monooxygenase (CYP1A) has an important function in the biotransformation of many xenobiotics, including polynuclear aromatic hydrocarbons and planar organochlorine compounds. The metabolism can cause to detoxification or activation to reactive intermediates. Exposure of fish leads to a receptor-mediated induction of CYP1A expression. In this study the effects of CYP1A induction, following exposure to benzo[a]pyrene (B[a]P), were studied in Sparus aurata gills and liver, the major organs of CYP1A activity in fish. CYP1A involved in the conversion of B[a]P to its electrophilic metabolites. Fish were exposed to waterborne B[a]P in DMSO 0.005% at concentrations of 2mg/L for 12, 24 and 72 hours; these data were compared with controls exposed only to the vehicle (DMSO 0.005%). The histological results revealed changes in gills and liver that were detected microscopically and evaluated with immunohistochemistry. In the gill filaments, cell proliferation, lamellar cell hyperplasia, lamellar fusion, lifting of the respiratory epithelium were observed. In the liver, there was vacuolization of the hepatocytes, sinusoidal congestion, necrosis of the parenchyma tissue, nuclear pyknosis, eosinophilic hepatocellular degeneration, pigment accumulation, an increase in the number and size of melanomacrophage centers. Immunohistochemistry evaluations revealed a marked immunoreactivity for CYP1A both in the liver and gills of fish, specially 72 hours after exposure to B[a]P. Strong CYP1A immunoreactivity was found in most cells in the secondary lamellae, whereas the primary lamellae were almost devoid of immunoreactivity. In conclusion, the present study points towards B[a]P is one of the most potent liver and gills CYP1A inducers, and considered as the most genotoxic compound. The biochemical responses of Sparus aurata gills and liver to exposure to B[a]P provide an interesting correlation with detoxification enzymes in agreement with B[a]P metabolites’ pivotal role.