Effects of Some Heavy Metal Pollutants On Glutathione Production In Clarias Gariepinus (Burchell, 1822) In An In Situ Bio-Assay In River Galma, Kaduna State, Nigeria

Abstract

Pollution of the aquatic media poses a lot of problems to the living biota within them and other organisms dependent on them for survival. Pollution from heavy metals are particularly deleterious as they are persistent within the ecosystem and have the tendency to bio-accumulate especially in higher vertebrates that depend directly or indirectly on them. Fishes possess different defensive mechanisms to counteract the impact of toxicants. This research focuses on the effects of some heavy metals on production of glutathione in Clarias gariepinus in an in situ bioassay in River Galma.120 samples (40 per exposure) of 20-45g size range of juveniles were exposed to the river environment for fourteen days in a cage system at five different locations along the river course for three different periods of the year. Glutathione were assayed for after the 7th and 14th day of exposure. Heavy metal (Pb, Cr, Cd, Zn and Mn) contents were also tested for in digested pooled samples of water, livers and gills of the fish. The results indicate significant difference in the levels of glutathione production in the gills in September at P<0.05 level of significance but not in the livers and kidneys. Glutathione production levels were highly significant in the gills and kidneys, and significant in the livers amongst the sites. Glutathione production levels were highly significant in the kidneys in all the months of exposures and locations. Highest mean values were obtained in all the organs of fish and in all the exposures from Kakeyi site. There were significant differences in the Chromium concentration in the gills and livers of the fish in all the exposures. There were strong positive correlation in glutathione production levels and Pb, Cr and Zn concentrations. Also, there was significant difference (P < 0.05) amongst the fish organs, water samples and Lead (Pb) concentrations. This research also established the presence of heavy metals examined in varying degrees of concentrations in water samples as well as in fish organs with the exception of Cadmium which was below detectable limit in fish organs. Glutathione can therefore, be used as biomarkers of pollution in River Galma to give early warning on environmental pollution to the community and policy makers.
Keywords: Oxidative stress, Glutathione, Reactive Oxygen Species, Heavy Metals, Biomarkers