Effects of alkalinity stress on serum physiological indexes of Gymnocypris przewalskii

【Objective】 The study was to figureout the effect of alkalinity on relevant physiological and biochemical parameters of Gymnocypris przewalskii, provide reference for developing the strategies of G. przewalskii to cope with the alkaline environment.【Method】 Using the serum of G. przewalskii as the research object,chronic alkalinity stress was carried out. The alkalinity gradually increased to the highest level and then decreased(without stress as the control). The changes in hormones,permeability,energy,oxidation,and immune indicators in the serum of each stress point were measured and analyzed.【Result】 Cortisol(COR),calcium(Ca²⁺),blood glucose(GLU),osmolality(OS),Na⁺/K⁺-ATPase(NKA),carbonic anhydrase Ⅱ(CAⅡ),carbonic anhydrase Ⅳ(CAⅣ),total protein(TP),albumin(ALB), globulin(GLOB),triglycerides(TG),alanine aminotransferase(ALT),aspartate aminotransferase(AST),catalase (CAT),glutathione peroxidase(GPX) and malondialdehyde(MDA) levels showed the same changetrend,all of which increased and then decreased with increasing alkalinity. And the trend decreased and then increased with decreasing alkalinity. COR showed extremely significant positive correlation with CAIV,TC,ALT,GPX,and MDA(P<0.01),and significant positive correlation with TP,GLOB,high-density lipoprotein (HDL-C),low-density lipoprotein (LDL-C), TG,and CAT (P<0.05,the same below). Insulin-like growth factorⅠ (IGF-Ⅰ),superoxide dismutase (SOD),sodium (Na⁺),alkaline phosphatase(AKP) and acid phosphatase(ACP) showed the same trend of decreasing followed by increasing regardless of alkalinity increase or decrease. Triiodothyronine (T3),total cholesterol (TC), HDL-C and LDL-C levels were negatively correlated with alkalinity,while creatinine (CREA) and total bilirubin (TBIL) levels were positively correlated with alkalinity. IGF-C was significantly positively correlated with T3. Thyroid hormone(T4) content and lactate dehydrogenase (LDH) activities increased,then decreased and then recovered with increasing alkalinity. Their activities decreased and then increased with decreasing alkalinity. Growth hormone(GH) and Cl^- content increased,then decreased,then increased with increasing alkalinity. They gradually increased with decreasing alkalinity. Prolactin(PRL) levels decreased slightly,recovered and then decreased again with increasing alkalinity,it increased rapidly and then recovered with decreasing alkalinity. Potassium(K⁺) concentration decreased with increasing alkalinity. K⁺ concentration increased and then decreased with decreasing alkalinity. Uric acid(UA) content decreased and then recovered with increasing alkalinity, its content gradually decreased with decreasing alkalinity. Urea(UREA) content increased,and then recovered,and continued to increase with increasing alkalinity, it continued to increase and then recovered with decreasing alkalinity.【Conclusion】 During alkalinity stress,COR plays a dominant role in G. przewalskii,with T3 and IGF-Ⅰ acting in concert and T4 regulating GH auxiliary,thereby maintaining humoral homeostasis in fish;the increase of TP, ALB,GLOB and TG contents,the decrease and later recovery of SOD activity,and the decrease and later recovery and later increase of AKP activity may be an important strategy for G. przewalskii to cope with the alkaline environment.