The effects of dietary selenomethionine on tissue-specific accumulation and toxicity of dietary arsenite in rainbow trout (Oncorhynchus mykiss) during chronic exposure

Abstract

The interactive effects of different doses of dietary selenium [as selenomethionine; 1.8 μg g⁻¹ (control), 10 μg g⁻¹ and 40 μg g⁻¹ diet] on the toxicity of dietary arsenic [as arsenite (As³⁺); 80 μg As per g diet] were investigated in rainbow trout over an exposure period of 30 days. Fish fed with As³⁺ alone showed an increased hepatic lipid peroxidation (LPO) and a concomitant decline in cellular redox potential (determined as GSH:GSSG) in the liver tissue relative to the control fish. Interestingly, fish fed with low (10 μg g⁻¹) or high (40 μg g⁻¹) concentration of dietary selenomethionine in combination with As³⁺ showed an even higher degree of hepatic LPO and a further decrease in GSH : GSSG molar ratio relative to the fish treated with As³⁺ alone. Our study also revealed that exposure to dietary selenomethionine (both at low and high levels) resulted in significantly higher levels of arsenic in target tissues (liver, kidney, and muscle) relative to fish treated with As³⁺ alone. Similarly, the synchrotron-based X-ray fluorescence imaging analysis also suggested a dose-dependent increase in the co-localization of arsenic and selenium in the brain of fish co-treated with dietary As³⁺ and selenomethionine. These observations suggested that selenomethionine facilitated arsenic deposition in the brain and likely in other tissues, possibly via bio-complexation. Overall, our findings indicated that elevated dietary selenomethionine can increase the tissue-specific accumulation and toxicity of As³⁺ in fish during chronic dietary exposure.