The Oxidative Stress And Histological Alteration Of Goldfish Carassius Auratus Exposed To The Contaminated Water Of The Yellow River

The activities and daily life of human beings make massive amounts of discharges and let them into the water body, which seriously pollutes the aquatic environment. Water is an important natural resource and the primary factor of organism survival. The contaminated water inevitably induced deleterious effects on human beings and the other organisms. It is necessary to detect and assess the water quality. Although, a routine chemical monitoring has been performed in many aquatic ecosystems, indeed, chemical analysis has some shortage, which only measures the toxic effects at point time, and gives no information of the changes during the past period. Moreover, the Wastewater often occurs as a complex mixture of chemical pollutants, chemical monitoring can detect neither adverse effect of chemical nor possible additive, synergistic or antagonistic events. On the contrary, biological monitoring can implement these defaults and demonstrates the toxic risk of both known and unknown contaminant on organisms and has a favor to evaluate the risk of the polluted waters.The two research areas of this present work were selected: the polluted area Baiyin Section of the Yellow River (BYSR) and the relatively unpolluted area Liujiaxia Section of the Yellow River (LJXR). Goldfish (Carassius auratus) as a bioindicator was chosen to assess the detrimental effects of water pollution on the levels of both histology and molecular biology, including DNA damage, lipid peroxidation, histological lesions and so on. The results show as follows:The pollution-related DNA damage level assessed by using the comet assay was significantly higher in the liver, kidney and gill of C. auratus from BYSR than those from LJXR, respectively(P<0.01), which indicated that the water in BYSR was strongly genotoxic to C. auratus. In comparison with the levels of DNA damage of liver, kidney and gill of C. auratus from BYSR in December 2005, April 2006 and June 2006 showed that the maximum values were in June 2006, these might be due to the reproduction period of C. auratus was during May and June and the reproduction period was more sensitive to water contamination.The enhanced content of MDA in the liver, kidney and gill of C. auratus from BYSR, respectively, which reflected that the pollutants in BYSR may cause lipid peroxidation due to toxic chemical accumulation in these organs, suggesting that fish exposed to contaminated water of BYSR were facing a condition of oxidative stress, but no statistically different (P>0.05). The degrees of MDA level of liver, kidney and gill of C. auratus from BYSR in December 2005, April 2006 and June 2006 showed the maximum values in June 2006, in accordance with the level of DNA damage. In addition, the maximum degrees of DNA damage and MDA level occurred in the gill of C. auratus, these might be due to gill organ of fish and other aquatic organisms at the first time exposed to the water body, so it was damaged more seriously than liver and kidney.Histological observation revealed that liver, kidney and gill were all damaged in BYSR. In liver, hepatocytes showed vacuolation, inflammation, degeneration and diffusing necrosis. In gill, with the main lesion being hypertrophy, hyperplasia and fragmentation of the gill epithelium, vague borders between the epithelial cells happened. Gill lamella bend in different degree, seriously lead to fusion of gill lamella. In kidney, with the main lesion being swelling, degeneration and necrosis of the renal tubular epithelial cell in different degree, disappearance of microvilli, presence of pyknotic nuclei, irregular arrangement of renal tubule-wall cells. The glomerular capsule showed various degree of kidney degeneration change, relatively decreasing or disappearance and enlarging of cisternae.In conclusion, the contaminated water in BYSR can remarkably damage the genetic material of C. auratus, cause lipid peroxidation of the goldfish's liver, kidney and gill, result in the histological alterations in different degrees and impair normal functions of liver, kidney and gill. The results do also imply that comet assay, MDA measurement, histological observation on liver, kidney and gill of C. auratus can be the sensitive indicators for monitoring the genotoxicity of complex aquatic environment.