Protein Profile and Mitochondrial DNA Analysis of Clarias Gariepinvs Surviving in the Korle Lagoon.

ABSTRACT
Studies have established the presence of some species including fish, in highly polluted water bodies. In order to develop a better understanding of their ability to survive in such environments, this work was undertaken to ascertain the extent of microsomal cytochrome
P450 induction, the modification of other proteins and the impact of the pollutants on the genetic material of the surviving organisms. In these studies, hepatic microsomal and cytosolic fractions were prepared from Clarias gariepinus, a fish species surviving in the highly polluted Korle lagoon. The same fractions were also prepared from fish samples obtained from the Weija Lake and fishponds at the Ministry of Food and Agriculture aquaculture demonstration centre (MOFA). The microsomal and cytosolic protein concentrations as well as activities of pollution-induced enzymes were assessed using ethoxyresorufin-O-deethylase (EROD), pentoxyresorufm-O-deethylase (PROD) and p-nitrophenol (PNP) hydroxylase assays. The values were compared among fish samples from the various water bodies before and after acclimatization to laboratory conditions.Cytosolic and microsomal protein profiles were obtained by separating the protein using
sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Mitochondrial DNA was extracted and purified by RNase digestion and the G+C base composition was determined. In samples both before and after acclimatization to laboratory conditions, cytosolic and microsomal protein concentrations were significantly higher for fish from the Korle lagoon compared to fish from MOFA and Weija Lake. The levels of EROD activities before and after acclimatization to laboratory conditions were significantly higher in fish obtained from the Korle lagoon compared to those obtained from Weija Lake and MOFA. The levels of PNP hydroxylase activities before acclimatization to laboratory conditions were significantly higher in fish obtained from the Korle lagoon compared to those obtained from Weija Lake but not those from MOFA. After depuration, the PNP hydroxylase activities were significantly higher for fish from the Korle lagoon compared to samples from both the Weija Lake and MOFA. EROD indicating CYP induction by polycyclic aromatic hydrocarbons (PAH), was approximately ten times higher in the samples from the Korle lagoon compared to the samples from the two other water
bodies, even after acclimatization to laboratory conditions. PROD activity, an indication ofCYP induction by phenobarbital and its related compounds was significantly lower in the Korle lagoon samples before and after acclimatization. These results indicate the induction of CYP 1A and CYP 2E by polycyclic aromatic hydrocarbons (PAH) and alcohols respectively in fish obtained from the Korle lagoon while induction of CYP 2B isozyme was depressed.The pattern of cytosolic and microsomal protein profile and the corresponding scan for samples from the various water bodies were similar but the intensity of bands and heights of peaks for fish obtained from the Korle lagoon were much higher even after depuration. Comparison of G+C base composition of mitochondrial DNA for C. gariepinus from the water bodies did not show any statistically significant differences. The study has shown that the induction of higher amounts of particular isozymes of cytochrome P450 such as the 1A and 2E isozymes to an extent that the levels are maintained even in the absence of the inducer might be the property enabling this organism to survive in the highly polluted Korle lagoon.