Effects Of Carbonate Alkalinities On Ammonia Excretion And Rh Gene Expression In Leuciscus Waleckii Dybowski

Leuciscus waleckii(Dybowski) belongs to Osteichthyes, Cypriniformes,Cyprinidae and Leuciscus, commonly known as Leuciscus waleckii, which is mainly distributed in Amur River, Liao River and some inland saline lakes of Inner Mongolia.It is also distributed in the Yellow River basin along the coast of the surrounding provinces(Henan, Shanxi, Shaanxi, Gansu and Qinghai). L. waleckii has strong tolerance of carbonate alkalinity and is able to survive in the inland saline lake, such as Dali Lake(CA 53.57, p H 9.6). These natural advantages make it become an ideal experimental animal for the study of the saline and alkali adaptability and the physiological mechanism of salt and alkalinity tolerance.1 、 This study has used artificial breeding F3 as experimental fish. Effects of different concentrations of carbonate alkalinities on oxygen consumption rate,ammonia excretion rate, plasma ammonia content as well as relative gene expression profile of Rh family in gill of Leuciscus waleckii Dybowski fish were studied using close water flow respiration measurement chamber. Oxygen consumption rate and ammonia excretion rate were significantly inhibited in different alkalinity conditions in comparison with those in control, and the lowest values of them were found in CA90, which indicated CA 90 may be the alkalinity limit for this species. Contrarily, the plasma ammonia content showed the opposite trend, first increasing then decreasing,and peaked in CA90. No significant difference was found for plasma ammonia content when CAranged from 0 to 50 m M, indicating this species has evolved to have specific ammonia excretion mechanism and thus helps maintain the low level of toxic ammonia form. Quantitative real-time PCR showed that Rhcg1 and Rhcg2 out of the four tested genes in Rh family may play an important role in the process of ammonia excretion in high alkaline stress. Energy metabolism(O:N) study found that L.waleckii Dybowsk did not consume too much energy to satisfy the energy needs within tolerance range(CA 0-70); however, when the environmental alkalinity was higher between 90 and 110, the body fat and carbohydrates became the main energysources to reduce protein consumption, which in turn decreased the poisonous ammonia excretion. This study served to elucidate the ammonia excretion strategy and possible physiological and molecular mechanism of ammonia excretion in L.waleckii Dybowski under high alkaline stress and it may provide evidence for aquaculturing L. waleckii Dybowski species in different carbonate alkaline waterbodies.2 、 Using hydrostatic water in sealed chamber for measurement, this study compared the change of oxygen consumption rate and ammonia excretion rate of L.waleckii Dybowski(Body weight: 72.62±3.70 g; fish no=15 from F3) exposed in high carbonate alkalinity water(CA 50 mmol/L) and high ammonia water(NH4CO3 1.5mmol/L) for 4 time points(2 h, 4 h, 6 h and 8 h) measurement. Oxygen consumption rate was significantly inhibited in carbonate alkalinity water and high ammonia water when compared that in fresh water(P<0.05). No significant difference of the oxygen consumption rate between carbonate alkalinity and ammonia water treated fish was detected for three tested time points, 4, 6, and 8 h. Results of ammonia excretion rate showed that compared with those in fresh water, the ammonia excretion rate of fish exposed in carbonate alkalinity water and ammonia water was significant inhibited(P<0.05). In ammonia water, the ammonia excretion rate of L. waleckii Dybowski for all 4 time points decreased, which had an extremely significant difference compared with fresh water and carbonate alkalinity water. This study reached lakedace in fresh water, high carbonate alkalinity(simulated natural water) and high ammonia stress changes in oxygen consumption rate and ammonia excretion rate, a preliminary understanding of L. waleckii up in the lake on environmental stress adaptability of the species breeding development in the inland region of the three north to provide basic information.3、In this study, L. waleckii were grown in carbonate alkalinity 50 mmol/L, and in fresh water, respectively. Using immunohistochemistry technique, the expression and localization of Rhcg1 protein in the gills of L. waleckii Dybowski was identified.The results showed that the base of gill lamellae in alkalinity exposed fish exhibited higher fluorescence intensity than that of fish from fresh water. This result may indicate that high carbonate alkalinity might promote higher expression of Rhcg1 gene.