Abstract:
The ability of African sharptooth catfish (Clarias gariepinus) in inducing cytochrome P-450 class
1A (CYP1A) and glutathione S-transferase (GST) biomarkers was determined in liver and gill filaments
after 4 days of waterborne exposure to the polycyclic aromatic hydrocarbon, benzo[a]pyrene (B[a]P). Male
(n=6) and female (n=6) fish were exposed to B[a]P added to the water (30 lg/l) corresponding to 5 mg/kg
total body weight. Five female and six male fish, exposed to acetone alone added to the water served as
controls. The 7-ethoxyresurufin-O-deethylase (EROD) activity was measured in hepatic microsomes and
gill filaments. In addition, GST activity was determined in the hepatic cytosolic fraction and fluorescent
aromatic compounds (FACs) in bile and biliverdin. Benzo[a]pyrene strongly induced EROD activities in
gill filaments of both sex. Levels of FACs per ml of bile were 17-fold higher in exposed fish compared to the
controls. Correlations between induction of EROD activities in gill filaments and liver and between
induction of EROD activities in gill filaments and levels of biliary FACs metabolites were strong. GST
activities in the hepatic cytosolic fraction were similar amongst the treated and control groups. This is the
first report on studies determining EROD activities in gill filaments and hepatic tissue, FACs in bile and
GST in hepatic tissues of C. gariepinus after waterborne exposure to B[a]P. The findings suggest that the gill
filament-based EROD assay in C. gariepinus can be used to monitor the pollution of AhR agonists in
aquatic ecosystems in eastern and southern African countries.
