Effects of dietary arginine supplementation on cytokine‐ and antioxidant‐related gene expressions in common carp ( Cyprinus carpio ) fingerling during ammonia toxicity

This study investigated the effects of dietary arginine supplementation on plasma ammonia and urea levels, and immune- and antioxidant-related gene expressions of common carp (Cyprinus carpio), exposed to ambient ammonia. Fish (10.5 ± 0.74 g) were fed diets containing arginine (0: control diet, 0.25: 0.25Arg and 0.5%: 0.5Arg) for 14 days and then subjected to ammonia exposure for three hours. The results showed that arginine significantly decreased plasma ammonia level, whereas increased the plasma urea level. Arginine supplementation significantly up-regulated head kidney il1b, il10, tnfa and liver sod, cat, gpx and gst gene expressions, whereas significantly down-regulated hsp70 gene expression in liver. Ammonia exposure led to a significant increase in plasma ammonia and urea levels. There were elevations in head kidney il1b, and liver sod, cat, gpx, gst and hsp70 gene expression in fish after challenged with ammonia. The interaction effects of arginine supplementation and ammonia exposure on head kidney il10, and liver gst and hsp70 gene expressions were observed, as arginine prevented ammonia-induced down-regulation in il10 expression, mitigated ammonia-induced up-regulation in hsp70 expression and intensified up-regulation in gst expression. In conclusion, it is suggested that two-week supplementation of arginine (0.5% of diet) is useful to mitigate the adverse effects of ambient ammonia when in the farm, common carp is at risk of ammonia toxicity.