Partial Amino Acid Metabolism and Glutamine Synthesis as the Ammonia Defensive Strategies During Aerial Exposure in Chinese Loach Paramisgurnus dabryanus

Abstract

The Paramisgurnus dabryanus was exposed to air to assess the changes in plasma, liver and muscle free amino acid (FAA) contents. The FAA concentrations in plasma, liver and muscle of P. dabryanus were significantly affected by aerial exposure (P < 0.05). After 12 h of aerial exposure, the plasma glutamate contents increased significantly (P < 0.05) and reached peak value at 24 h of air exposure. With increasing air exposure time, the plasma alanine contents increased significantly and more dramatically than the control values (P < 0.05). From 24 to 48 h of aerial exposure, the liver free glutamate contents increased significantly and reached the peak value at 48 h of air exposure (P < 0.05). The liver free alanine contents in air exposure group were markedly higher than these values in the control group (P < 0.05). After 72 h of air exposure, the muscle free glutamate contents increased markedly (P < 0.05) and were significantly higher than the control values (P < 0.05). The muscle free alanine contents remained at constant values during the first 12 h of aerial exposure (P > 0.05), thereafter, these concentrations increased significantly until the end of experiment (P < 0.05). Our results showed that glutamate and NH4+ could be used to synthesize glutamine via glutamine synthetase to convert internal ammonia into non-toxic glutamine in P. dabryanus during air exposure. Furthermore, the P. dabryanus could catabolize several certain amino acids, leading alanine form to reduce endogenous ammonia production. The decrease in tissue free glutamate, arginine and proline in P. dabryanus indicated that these certain amino acids should be the starting substrate to be converted to alanine and energy.

High concentrations of environmental ammonia induced changes in large‐scale loach (Paramisgurnus dabryanus) immunity

“…Exposure to heavy metals also caused a significant increase in serum total protein and albumin contents in Cyprinus carpio (Gopal et al, 1997). Because the energy requirements of large-scale loach increase significantly after ammonia exposure (Zhang et al, 2019), the increased protein contents in large-scale loach may serve as an energy source. However, intraperitoneal injection of ammonia acetate in Pelteobagrus fulvidraco significantly reduced the serum total protein, albumin, and globulin contents, which was mainly due to the different experimental design where fish were fed twice a day (Zhang et al, 2018).…”

“…According to the China Fisheries Statistics Yearbook 2020, the production of Chinese loach in 2019 was 356,900 tons. As a typical air-breathing fish (Zhang et al, 2016), large-scale loach has a variety of effective strategies for ammonia detoxification (Zhang et al, 2019). Ammonia, as an environmental stressor, induces a strong stress response in large-scale loach (Ding et al, 2019).…”

Effects of Acute Ammonia Stress on Antioxidant Responses, Histopathology and Ammonia Detoxification Metabolism in Triangle Sail Mussels (Hyriopsis cumingii)

“…Moreover, ALT and AST can decompose glutamate into alanine and aspartate without releasing ammonia [6,24]. According to previous studies, there was another main ammonia detoxification strategy that partial catabolism of some amino acids led to the formation of alanine without releasing ammonia in fish [6].…”

“…Ammonia is also the nitrogen end product of protein and amino acid metabolism, which is excreted into the surrounding environment across the gills in teleosts [6,15]. However, under certain circumstances such as high environment ammonia (HEA), aquatic animals are confronted simultaneously with the accumulation of endogenous ammonia and uptake of exogenous ammonia, which will result in the inhibition of ammonia excretion [24]. There are many mechanisms to cope with high internal ammonia in adverse environments, such as the synthesis of less-toxic glutamine and urea [25].…”

“…There are many mechanisms to cope with high internal ammonia in adverse environments, such as the synthesis of less-toxic glutamine and urea [25]. Previous studies suggested that glutamine synthesis was an effective ammonia detoxification strategy in fish, such as Oncorhynchus mykiss [25] and Paramisgurnus dabryanus [6,24]. At present, the study of ammonia on freshwater mussels was mainly focused on toxicity assessment, filtration behavior, hemocyte status, DNA damage and apoptosis, cellular energy allocation, and so on [26][27][28][29].…”