Assessment of Responses of Common Carp, Cyprinus carpio, Exposed to Sub-Lethal Concentrations of Lead, by Molecular and Mucosal Biomarkers

Abstract

Heavy metals are one of the most persistent pollutants in waters, and molecular biomarkers as bioindicators could uncover early warning signals of stress suffered by organisms exposed to these pollutants. This research was conducted to explore the impact of lead contaminant on expression levels of hsp70 gene as well as protein pattern and innate immune indicators of skin mucus in Common carp as a biological model. The fish were exposed to different concentrations of Pb(NO3)2 as a source of lead (0, 7.875, 15.75, and 31.5 mg/L of lead) for 14 days. After the completion of the experiment, the liver and gill tissue plus mucus samples were collected from the fish. Next, the effects of exposure to sublethal doses of lead were investigated on expression levels of hsp70 gene, protein pattern, and innate immune indicators of skin mucus. The results indicated that the expression level of hsp70 gene significantly increased (at 7.5% & 30% LC50) in the liver tissue compared to the control group (P<0.05). The protein pattern of treatment samples was different from that of the control group. Also, in the mucus innate immune parameters, the levels of alkaline phosphatase increased significantly at high concentrations of lead contamination in comparison with the control group (P<0.05). The protein levels first revealed an ascending trend (P<0.05), and then a descending trend (at 30% LC50), though it was not a significant downward trend compared with the control group (P>0.05). The results suggested that these physiological indicators in Cyprinus carpio could be used as molecular and mucosal biomarkers for ecotoxicological studies.