Sublethal Effects of Ternary Mixtures of Polycyclic Aromatic Hydrocarbons on Selected Liver Biomarkers of Clarias gariepinus

Abstract

The effect of ternary mixtures of polycyclic aromatic hydrocarbons in Clarias gariepinus was investigated. Apparently healthy juvenile fish (n = 90) weighing 19.7±1.8 g were exposed to sublethal concentrations of naphthalene, phenathrene and benzo[a]pyrene over a period of 35 days after which liver biomarker analyses were carried out on blood plasma fraction. The observed total plasma protein was 35.1 g/L while the albumin and total bilirubin concentrations were 15.9 g/L and 4.6 μmol/L respectively. The plasma concentrations of the liver enzymes were 25.27 IU/L, 9.37 IU/L, and 28.01 IU/L for alanine transaminase (ALT), aspartate transaminase (AST), and alkaline phosphatase (ALP) respectively. While there were significant declines in plasma total protein and albumin, significant elevation was observed in plasma total bilirubin. Significant increases were also observed in the activities of the liver enzymes, alanine transaminase (ALT), aspartate transaminase (AST) and alkaline phosphatase (ALP). Exposed liver and gill sections showed histopathological alteration. There was steatosis accompanied with moderate dense infiltrates in the liver while the gills showed channel dilatations with hyperplasia. Findings from this study suggest that PAH mixtures cause changes in the activities of liver metabolic enzymes as well as alter the normal architecture of liver and gills in exposed aquatic organisms.