Effect of ammonia nitrogen on the detoxification metabolic pathway of cuttlefish (Sepia pharaonis)

The goal of this research was to explore the detoxification metabolic pathway and regulatory mechanism of the cuttlefish (Sepia pharaonis) under ammonia nitrogen stress. This study investigated the ammonia and urea contents in the hemolymph and liver and the amino acid contents in the liver using high-performance liquid chromatography (HPLC) and examined the changes in the activities and mRNA expression of key enzymes in the ammonia nitrogen metabolic pathway under different ammonia nitrogen stress concentrations (1 mg/L, 3 mg/L, 6 mg/L and 12 mg/L). The main conclusion was that the key indices of the urea metabolic pathway showed obvious time-concentration effects under ammonia nitrogen stress. An ornithine-urea cycle metabolic pathway was confirmed to exist in cuttlefish at the transcriptional and metabolic levels. Under low ammonia nitrogen stress, cuttlefish can detoxify ammonia nitrogen into urea through urea metabolism. However, the metabolic pathway of the urea cycle is inhibited under high ammonia nitrogen stress (>= 12 mg/L). Second, under ammonia nitrogen stress, the contents of glutamine, taurine, proline, glycine (except under high concentration stress), citrulline and tyrosine in the liver tissue increased significantly (P < 0.05). Aspartic acid and alanine initially increased and then decreased with the concentration of ammonia nitrogen. In summary, under ammonia nitrogen stress, cuttlefish may utilize the urea and amino acid metabolic pathways. Converting ammonia nitrogen to urea and amino acids (glutamine, taurine, proline, glycine, aspartic acid, alanine, citrulline and tyrosine) reduces the ammonia nitrogen content in the body. However, under high ammonia nitrogen stress, the urea cycle pathway and some amino acid metabolic pathways (such as aspartic acid and alanine) are inhibited.

Automated summary

The goal of this study was to explore the detoxification metabolic pathway and regulatory mechanism of the cuttlefish under ammonia nitrogen stress. The study found that the cuttlefish can detoxify ammonia nitrogen into urea through urea metabolism and utilize amino acid metabolic pathways to reduce ammonia nitrogen content in the body. However, these pathways are inhibited under high ammonia nitrogen stress.