RESUMO
Glycaemia, a classical indicator of stress, xanthine oxidase and aldehyde oxidase which are involved in phase I detoxication were investigated in two different fish species from two rivers with different pollution levels in the Western Niger-Delta. Four sampling zones covering the entire lengths of Warri and Ethiope Rivers respectively were used in this study. For each species of fish five were obtained from a sampling zone in a river. Blood glucose was significantly higher (P < 0.001) in M. electricus from Warri River (82.13 +/- 5.50 mg cm(-3)) compared to the same species from Ethiope River (36.47 +/- 1.49 mg cm(-3)). With the same parameter a similar profile was observed for C. gariepinus; Warri River (56.92 +/- 10.31 mg cm(-3)); Ethiope River (37.65 +/- 0.90 mg cm(-3)) which was also significant (P < 0.01). The activity of xanthine oxidase in M. electricus from Warri River (255.80 +/- 41 it mol cm(-3)) was significantly higher (P < 0.001) compared to the value obtained for the same species (108 +/- 22.36 micro mol cm(-3)) from Ethiope River. Also the activity of xanthine oxidase in C. gariepinus from Warri River (197 +/- 34.65 micro mol cm(-3)) was significantly higher (P < 0.001) when matched with the value obtained for the same species (78.40 +/- 26.84 micro mol cm(-3)) from Ethiope River. That blood glucose level was related to xanthine oxidase activity in the two fish species from Warri River was supported by the high positive correlation between these two parameters (M. electricus. r = 1: C. gariepinus, r = 0.71). The activity of aldehyde oxidase in C. gariepinus from Warri River (143.80 +/- 28.45 micro mol cm(-3)) was significantly higher (P < 0.001) compared to the value obtained for the same species (61.20 +/- 15.21 micro mol cm(-3)) from Ethiope River. A similar profile in aldehyde oxidase activity observed for M. electricus; Warri River (130 +/- 28.39 micro mol cm(-3)); Ethiope River (89 +/- 19.70 micro mol cm(-3)) but an inferior statistical variation (P < 0.05) was obtained. The results obtained in this study indicate that the level of xanthine oxidase in M. electricus is a more specific marker and to a lesser extent its activity in C. gariepinus in monitoring environmental stress due to pollution.
