The Expression Of AQPs And Hypoxia-related Proteins In The Kidney Of The Tibetan Sheep

As a typical plateau animal,the Tibetan sheep lived in the plateau hypoxi area which is cold and drought,showed special adaptive changes even in the structural characteristics.As the vital organ regulating water metabolism,kidney also plays an important role in oxygen transport.In this project,the kidney of Tibetan sheep were studied,and compared with Small-tailed Han sheep,in order to provide a theoretical basis for the morphological structure and related functional changes of Tibetan sheep adapting to the plateau environment.The kidney tissues of Tibetan sheep and Small-tailed Han sheep were collected,paraffin sectioned,HE staining,Masson staining and PAS staining were used to observe the structural differences and glycogen distributions,and the expression and distribution of AQPs(Aquaporins,AQPs)especially AQP1,AQP2,AQP3,AQP4 and high altitude hypoxia related proteins HIF-1α(Hypoxia Inducible Factor-1α),HSP70(Heat Shock Proteins)and EPO(Erythropoietin)were observed by immunohistochemical SP method while fluorescence quantitative PCR were used to detect their mRNA.The results were showed as follows:1.The renal capsule of Tibetan sheep showed obvious smooth muscle layer,the glomerular area of Tibetan sheep was 10716.55±2136.72μm,the average diameter of glomerulus was 115±10.30μm,which was significantly larger than that of Small-tailed Han sheep(P<0.05),the number of glomeruli per unit area was 8.62±1.75 A/mm2,the diameter of proximal tubule is 43.03±6.67μm,the diameter of distal tubule was 29.01±3.51μm,the diameter of collecting duct was 45.44±5.78μm,showed no significant difference between Tibetan sheep and Small-tailed Han sheep(P>0.05).2.In Tibetan sheep kidney,AQP1 protein was mainly distributed in proximal tubule,thin segment and straight small vessel,and the expression intensity of proximal tubule was the highest;AQP2 protein was mainly distributed in collecting duct and distal tubule,and strongly expressed in collecting duct;AQP3 protein was mainly distributed in proximal tubule,distal tubule and collecting duct,and widely distributed;AQP4 protein was mainly distributed in the basement membrane of main cell of collecting tubule,and a little expression was found in proximal tubule microvilli.The expression of AQP1 gene in renal medulla of Tibetan sheep was the highest,significantly higher than that of Small-tailed Han sheep(P<0.05),and there was no significant difference in cortical;The expression of AQP2 gene in renal cortex of Small-tailed Han sheep was significantly higher than that of Tibetan sheep(P<0.05),and the expression of AQP2 gene in renal medulla of Tibetan sheep was significantly higher than that of Small-tailed Han sheep(P<0.05);The expression of AQP3 gene in renal cortex of Small-tailed Han sheep was the highest,significantly higher than that of Tibetan sheep(P<0.05),and the expression in renal medulla of Tibetan sheep was significantly higher than that of Small-tailed Han sheep(P<0.05);The expression of AQP4 gene in renal medulla of Tibetan sheep was the highest,significantly higher than that of Small-tailed Han sheep(P<0.05),and the expression of AQP4 gene in renal cortex of Small-tailed Han sheep was higher than that of Tibetan sheep(P<0.05).3.HIF-1α protein was expressed in the cytoplasm and nucleus of renal tubules,glomeruli and collecting ducts,obviously in renal tubules,but less in collecting ducts,and the expression intensity in nuclei was higher than that in Small-tailed Han sheep.HSP70 protein was expressed in the cytoplasm and nucleus of renal tubules,glomeruli and collecting tubules,and was strongly expressed in proximal tubules and distal tubules,but weakly expressed in collecting tubules,and the expression intensity in nuclei was higher than that in Small-tailed Han sheep.EPO protein was strongly expressed in proximal tubules and distal tubules,but lower in collecting tubules,and mainly expressed in cell membrane,but less in cytoplasm.The expression of HIF-1α gene was the highest in medulla of Small-tailed Han sheep,the second in medulla of Tibetan sheep,the third in renal cortex of Tibetan sheep,and the lowest in renal cortex of Smalltailed Han sheep(P<0.05);The expression of HSP70 gene was the highest in the medulla of Tibetan sheep,followed by the cortex of Small-tailed Han sheep,and the expression of renal medulla of Tibetan sheep was significantly higher than that of Small-tailed Han sheep(P<0.05);The expression of EPO gene in renal cortex and medulla of Tibetan sheep was higher than that of Small-tailed Han sheep,and the expression of EPO gene was high in renal cortex of Tibetan sheep(P<0.05).In summary,in order to adapt to the special environment of hypoxia,cold and drought at high altitude,the area of glomeruli of Tibetan sheep is larger,and the expression of AQPs is significantly higher than that of small tail Han sheep at low altitude.It is inferred that Tibetan sheep has higher blood filtration efficiency,and can reabsorb water in urine more efficiently and maintain water balance in the body.Abundant HIF-1α,HSP70 and EPO in the kidney make the kidney better adapt to the cold and drought environment of hypoxia at high altitude,enhance cell activity,antioxidant capacity,maintain the normal function of organs,increase the number of red blood cells and hemoglobin content,and enhance the capacity of oxygen transport.