Fish Liver Biomarkers for Heavy Metal Pollution: A Review Article

Heavy metals as dangerous and long lasting pollutants in environment have been widely studied and monitored. Liver is the most important organ in storage and detoxification of these pollutants. Assessment of indicators, including changes in intermediate active components between the liver and pollution effect, provide sensitive liver biomarkers and can be a suitable index for health condition of fish. In addition, fish liver is a favorite model to study interaction between environmental factors and liver structure and performance. This review studies variety of liver biomarkers in molecular- cellular (damage to chromosome, DNA and lysosome; increasing metallothionein and ferritin levels), biochemical-physiological (transaminase enzymes and oxidative enzyme parameters) and morphological-histopathological levels, and investigates advantages and disadvantages of these levels. Moreover, restrictions and landscape in the future is discussed for these biomarkers exposed to heavy metals pollution. There are many liver biomarkers that can be used for identification of initial heavy metal pollution, assessment of health condition of fish and ability of fish to defense against pollution challenges. Some of these biomarkers are special for heavy metal pollution while the others are non-specia

Comparison of waterborne and intraperitoneal exposure to fipronil in the Caspian white fish (Rutilus frisii) on acute toxicity and histopathology

Fipronil is an effective insecticide widely used in agriculture with potential ecotoxicological consequences. The median lethal dose (LD50) and concentration (LC50) of fipronil in 16.3 g Caspian white fish, Rutilus frisii kutum fingerlings were determined. To determine the LD50, a total of 133 fish were assigned to 19 tanks (7 fish/tank) including one control and 6 treatment groups (300, 450, 550, 650, 750, 850 mg/kg). Fish were injected intraperitoneally and monitored at 96 h. The LD50 of fipronil was 632 mg/kg suggesting it was slightly toxic to the Caspian white fish. To determine LC50, 114 fish were assigned to 19 tanks (6 fish/tank) including one control and 6 treatment groups (300, 400, 500, 600, 700, 800 μg/L). The LC50 of fipronil was 572 μg/L, which was highly toxic to the fish. The degree of tissue change (DTC) in vital organs from moribund fish exposed via waterborne exposure showed severe damage (DTC: 71 ± 52 for 700 μg/L) in the gill, including aneurisms, extensive fusion and necrosis. The fish exposed through the intraperitoneal route seemed to have severe lesions (DTC: 66 ± 50 for 750 mg/kg) in the kidney, involving hemorrhage, tubular degeneration and necrosis. The liver had no significant differences in DTC values between the two routes and showed pyknosis and sinusoid dilation. Hematoxylin and eosin staining did not show any histological alterations in the brain but nissl staining showed some alterations in distribution of purkinje cells. Generally, this study showed that the route of exposure to fipronil not only affects its acute toxicity but also determines the main target organs of toxicity and histopathological alterations in Caspian white fish. Keywords: Fipronil, Caspian white fish, Acute toxicity, Administration rout

CYP1A gene expression as a basic factor for fipronil toxicity in Caspian kutum fish

The aim of this study was to assess the effects of fipronil insecticide on the Caspian kutum fish at different levels of biological organizations and to find possible relationship between these biomarkers. Different doses of fipronil (65, 130 and 200 mg/kg) were intraperitoneally administered to the fish for 2 weeks. After 7 and 14 days of exposure, alterations in organ-somatic index, tissue and DNA structure, oxidative stress and CYP1A gene expression in gill, liver, brain and kidney were studied. Determination of these parameters in the liver showed that the degree of tissue change (DTC), comet tail, superoxide dismutase (SOD) and relative CYP1A mRNA expression increased mostly in a time dependent manner whereas in the kidney increased mostly in a dose dependent manner. These parameters in the gill increased more in time and dose dependent manner. Apart from the changes in CYP1A expression and oxidative stress, no alterations was observed in the brain. Multiple regression analysis showed that the CYP1A had the most correlation with the organ-somatic index (R2 = 0.76) and comet tail (R2 = 0.89) in the liver, and with DTC (R2 = 0.93) and oxidative stress (R2 = 0.87) in the kidney. Generally, this study showed that CYP1A gene expression can be considered as one basic factor for fipronil toxicity in this fish. However, other possible factors also should be considered for future research. Keywords: CYP1A gene, Oxidative stress, Comet assay, Fiproni

Effects of Naphthalene on Plasma Cortisol and Thyroid Levels in Immature and Mature Female Klunzingeri Mulet, Liza klunzingeri

Background: Polycyclic aromatic hydrocarbons (PAHs) such as naphthalene (NAP) are organic pollutants that have spread widely in littoral marine ecosystems. We aimed to study the effect of acute and prolonged exposure to naphthalene (NAP) on plasma cortisol and thyroid levels in mature and immature Liza klunzingeri mulet. Methods: In acute stress experiment, the treatment group received 2μl g-1 sunflower oil containing NAP (50 mg kg-1) intraperitoneally and the controls were injected with sunflower oil alone (2μl g-1). Blood samples were obtained from both groups after 3 h. In prolonged stress experiment, 10 μl g-1 of coconut oil containing NAP (50mg kg-1) was implanted and blood samples were obtained 72 h after injection. Results: Both the acute and prolonged exposure induced significant increase in cortisol and a significant decrease (P<0.05) in thyroid hormone T4 levels. Thyroid T3 hormone levels only decreased significantly (P<0.05) after prolonged exposure. Acute exposure resulted in significant decrease (P<0.05) in T3/T4 ratio only in immature fish. On the other hand, prolonged stress increased T3/T4 ratio in immature fish. Conclusion: Changes in the plasma levels of these hormones indicate low physiological capacity and survival potential of fish in waters polluted with naphthalene