A two-stage study was carried out to test the mechanism of
arginase in
ammonia detoxification of yellow catfish. At stage 1, fish was injected lethal half concentration
ammonium acetate and 0.9%
sodium chloride respectively every 12 h in six replicates for 72 h. The result found that no significant different in serum
ammonia contents of fish in
ammonium acetate group at hours 12, 24, 36, 48, 60 and 72. At stage 2,
ammonium acetate group was split in two, one continued to injected with
ammonium acetate (NH3 group) and the other with
ammonium acetate and
valine (an inhibitor of
arginase; Val group);
Sodium chloride group also was split in two, one continued to injected with
sodium chloride (NaCl group) and the other with
sodium chloride and
valine (NaCl + Val group). The experiment continued for 12 h. Serum
ammonia and liver
arginine contents of fish in Val group were higher than those of fish in NH3 group; Compared with NaCl group,
arginase activity and ARG 1 expression in liver of fish in Val group were lower; Fish in NaCl and NaCl + Val groups had the lowest serum
superoxide dismutase activities,
malondialdehyde,
tumor necrosis factor-α,
interleukin 1 and 8 contents, TNF-α,
IL-1 and
IL-8 expressions than fish in NH3 and Val groups, and had the higher
lysozyme activities,
complement 3 and 4 contents. This study indicates that
ammonia poisoning would lead to oxidative damage, immunosuppression and
inflammation in yellow catfish;
Arginase may be an important target of
ammonia toxicity in yellow catfish; Exogenous
arginine supplementation might alleviate the symptoms of
ammonia poisoning in yellow catfish.