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Silymarin, an extract from "milk thistle" (Silybum marianum) plant is traditionally used as herbal medicine. The present study was conducted to investigate the clinical effects and possible side effects of silymarin on biochemical blood parameters of rainbow trout (Oncorhynchus mykiss). Fishes were treated with 0 (control), 100, 400, and 800 mg of silymarin per kg of food during 4 weeks. Plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), creatine kinase (CK), glucose, total protein, creatinine, triglyceride, cholesterol, urea, uric acid and liver cellular total antioxidant, and protein content were measured after 7, 14, and 28 days of silymarin treatment. The results showed that oral administration of silymarin in fish significantly reduced plasma glucose and cholesterol levels and relatively increased plasma total protein and globulin concentrations (P < 0.05). Increasing plasma albumin levels indicate the important role of albumin in drug transportation in circulatory system of fish. Silymarin also stabilized cellular membrane structure and regulated the levels of AST, ALT, ALP, CK, and LDH activity. In conclusion, on the basis of these results, oral administration of silymarin up to 400 mg per 1 kg of food has no side effect on blood biochemical and clinical parameters of fishes. However, oral administration of 800 mg/kg- of silymarin caused cytotoxicity and modifications in blood biochemical parameters of fish.

The organophosphate insecticide diazinon is widely used to control pest in Iran. The purpose of the present study was to investigate the antioxidant and histopathological changes in the liver tissue of rainbow trout (Oncorhynchus mykiss) exposed to 0.1 and 0.2 mg/L of a commercial formula of diazinon for a period of 28 days. Antioxidant enzyme activities--catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase--were determined after 7, 14 and 28 days of exposure. Histopathological analyses were performed at the 28th day. All antioxidant enzymes were induced after 7 days of diazinon treatment in both concentrations of diazinon. Catalase and superoxide dismutase maintained elevated activities during all the treatment period. Glutathione peroxidase activity returned to the control values at the 14th day, decreasing to values below control at the 28th day in both diazinon concentrations. Glutathione reductase maintained increased activities at the 14th day in the 0.1 mg/L diazinon, decreasing to control values at the 28th day. In the 0.2 mg/L group, the activity returned to control values at the 14th and decreased below the control at the 28th day. Total antioxidant capacity of hepatocytes significantly decreased in fishes exposed to diazinon during all experimental periods. Hypertrophy of hepatocytes, vacuolization of cell cytoplasm and hepatocyte cloudy swelling were observed in the liver tissue of fish exposed to both concentrations of diazinon. The results showed that diazinon altered the activity of antioxidant enzymes and the cellular total antioxidant capacity inducing oxidative stress and cellular damage in hepatocytes evidenced by histopathological analysis.

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Ataeimehr B. 2012. Evaluation of the immunomodulatory effects of silymarin extract (Silybum marianum) on some immune parameters of rainbow trout, Oncorhynchus mykiss (Actinopterygii: Salmoniformes: Salmonidae). Acta Ichthyol. Piscat. 42 (2): 113-120.Background. Herbal medicines are increasingly used for their effects on the immune system. Silymarin, a mixture of flavonolignans from the seed of milk thistle (Silybum marianum), is used in treatment of liver disease, food and drug poising, and foetal diseases such as viral hepatitis, diabetes, and ischemia. Although, immunostimulant effects of the dietary silymarin were studied on different experimental animals, no information is available about the effects of silymarin on immune parameters of fish. The presently reported study was conducted to investigate the immunomodulatory effects of silymarin on some immunological and haematological parameters of rainbow trout. Materials and methods. Juvenile rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), were maintained in 1000 L fiberglass tanks at 15 ± 2ºC supplied with systems of water recirculation and aeration. Silymarin extract incorporated into diets (0.0, 0.1, 0.4, and 0.8 g of per 1 kg of feed) of fish. The trout were fed silymarin-supplemented diet for 30 days. Haematological parameters, such as red blood cell count (RBC), white blood cell count (WBC), haematocrit (Hct), haemoglobin (Hb), differential leukocyte-and immunological parameters such as peroxidase, lysozyme, and complement activities, total protein, albumin and globulin levels were measured on day 7, 15, and 30 days of silymarin treatment. Results. The results indicated that oral administration of silymarin in fish, after 15 and 30 days of experimental periods, might enhance haematological and immunological parameters including lysozyme and complement activities, total protein and globulin levels, compared to the controls. Conclusion. The results suggest that oral administration of silymarin may be useful to strengthen the immune system in rainbow trout.