Diazinon (Organophosphorus insecticide) can cause reactive oxidative stresses during metabolism of aquatic organisms. The study presented here aimed to investigate the antioxidant effect of vitamin C on antioxidant enzyme activities and lipid peroxidation in rainbow trout exposed to subchronic dosage diazinon. A total number of 360 Oncorhynchus mykiss were allocated into four treatment groups (with three replicates): control; diazinon (0.1 mg L 1); vitamin C (300 mg kg 1 in diet) plus diazinon (0.1 mg L-1), and vitamin C (1000 mg kg-1 in diet) plus diazinon (0.1 mg L-1). After two and four weeks, blood samples were collected and superoxide dismutase, catalase enzymes, total antioxidant capacity and malondialdehyte index were measured. The specimens exposed exclusively to diazinon showed a significant decrease in superoxide dismutase and total antioxidant capacity activities and also an increase in catalase activity and malondialdehyde index compared to those of the control group. The changes in oxidative stress parameters may be related to destructive free oxiradicals such as superoxide and hydroxyl radicals produced in diazinon metabolism. In conclusion, vitamin C moderated activity of the antioxidant enzyme, increased the total antioxidant capacity, and decreased cellular damages caused by destructive lipid peroxidation process in presence of diazinon.

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Biochemical parameters are appropriate biomarkers to assess the effects of pesticides on an aquatic ecosystem. Diazinon is an organophosphate pesticide whose metabolism in fish body produces reactive oxygen species that can cause oxidative stress. In this study, Oncorhynchus mykiss were allocated into four treatment groups (with three replicates): control; Diazinon; vitamin C + diazinon, and vitamin E,selenium + diazinon. Blood samples were obtained after two and four weeks and superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (TAC), and malondialdehyde (MDA) were measured. SOD activity was significantly lower in diazinon-exposed fish than in the control group. However, there were no differences between the two supplemented groups and the control group in this regard. CAT activity was significantly higher in all three diazinon-exposed groups compared to the control group. However vitamin E, selenium had the least difference with the control group. Maximum and minimum TAC were observed respectively in fish supplemented with vitamin E, selenium and those only exposed to diazinon. The diazinon group also had the highest MDA levels. The two supplemented groups and the control group had no significant differences in MDA levels. These findings highlighted the antioxidant effects of supplementation with vitamin E, selenium or vitamin C against free radical produced during the metabolism of diazinon. Meanwhile, the combination of vitamin E, selenium had higher antioxidant effects than vitamin C. Moreover, SOD, the first defensive barrier against superoxide radicals, and MDA, an index of cellular damage induced by hydroxyl radicals, are the most suitable indicators to assess the effects of diazinon.

The present research has investigated the effect of Lactobacillus farraginis (LF) and Enterococcus durans (ED), isolated from kefir, as probiotic on innate immune parameters and expression of IL-1β and TNF-1α lysozyme genes in the intestine, as well as resistance to the Lactococcosis in rainbow trout. Four hundred and eighty juveniles (41.9 ± 2.4 g) were divided into eight groups with three replications, including the control, LF1 and LF2 supplemented with 10 7 and 10 8 Cfu/g feed of each strain, Bactocell equivalent to 10 10 , ED1 and ED2 with 10 7 and 10 8 Cfu/g feed of each strain, combination supplements LF1+ED1 and LF2+ED2 with 5 × 10 6 and 5 × 10 7 Cfu/g feed of each strain. Compared to control, a significant increase (p < 0.05) was observed in in serum lysozyme, ACH50, C3 and C4, total antibody, bactericidal activities and blood phagocytosis in LF2, Bactocell, LF2+ED2, and ED2 treatments. Besides, lysozyme gene expression in the intestinal tissue of fish treated with LF2, ED2, and Bactocell significantly increased (p < 0.05). A significant increase in TNF-1α gene expression was also observed in all treatments except LF1 and ED1 (p < 0.05). Moreover, a significant increase in the level of IL-1β gene expression was observed in all groups, except for ED1 and LF1+ED1, in comparison to the control treatment. After challenge with Lactococcus garvieae, the lowest mortality percentages were recorded for LF2, Bactocell, LF2+ED2, and ED2 treatment compared to the control. The results suggest beneficial effects of kefir derived LAB strains on immune responses, immune-related genes expression, and disease resistance in rainbow trout.