Comparative Study On Expression Of Aquaporins In Lepus Yarkandensis And Oryctolagus Cuniculus Several Organs

Lepus yarkandensis is endemic species of Xinjiang,adapted to the peculiar arid environment of Xinjiang.The mechanism of environmental adaptation of L.yarkandensis is rarely reported.Aquaporins(AQPs)are a family of membrane water channels,which facilitate water transport across cell membranes.AQPs are present in numerous tissues and organs and play an important physiological function in the body,such as kidney AQPs are involved in renal tubule water permeability and urinary concentration,lung AQPs are involved in hydrating the inspired airstream,AQPs in the digestive tract are involved in the secretion of digestive juice and reabsorption of water in feces.To explore the mechanism of L.yarkandensis adaptation to the arid environment,because of the important physiological function of AQPs in tissues and cells,it is necessary to study the role of AQPs in L.yarkandensis adaptation to the arid environment.Therefore,it is necessary to understand and determine the distributions and expression of AQPs in L.yarkandensis tissues.In the study,firstly differential expression gene(DEGs)in kidneys of L.yarkandensis and Oryctolagus cuniculus were analysed by gene expression profiling chip.the DEGs related to water retention were screened out,the results revealed that there was a significant difference in kidney AQPs transcription between L.yarkandensis and O.cuniculus.Next,the full cDNA sequence of AQP2 gene of L.yarkandensis was obtained by rapid-amplification of cDNA ends(RACE),the amino acid sequence alignment showed that the identity of AQP2 amino acid sequence among L.yarkandensis and O.cuniculus to be 99%.Then,the distributions and expression of AQPs in tissues and organs maintainning water of O.cuniculus and L.yarkandensis were examined by immunohistochemistry(IHC),quantitative Real-time PCR(qRT-PCR)and western blot.In the kidney,AQP1 was abundance in the capillary endothelial cells in glomerulus and epithelial cells in proximal tubule and descending thin limbs,AQP2 was in the apical plasma membrane of principal cells in collecting duct,AQP3 and AQP4 were present on the basolateral plasma membrane of principal cells in collecting duct.Our results also showed a marked increase in the expression levels of AQP1,AQP2,AQP3 and AQP4 in L.yarkandensis kidneys compared with O.cuniculus,this promoted the ability of renal tubules to absorb water from tubular fluid and reduced water loss.In the lung,AQP1 was localized to the endothelial cells of capillaries and venules that surround terminal bronchiole and alveolus,AQP5 was localized to the ciliated columnar cells in terminal bronchiole and the alveolar type I cells in alveolus.Our results also suggested a significant increase in AQP1 and AQP5 levels in distal lung of L.yarkandensis compared with O.cuniculus,this helped to compensate for water loss on the airway surface caused by inhalation of dry air.In the digestive tract,AQP1,AQP3 and AQP4 were in gastric pits,fundic glands,small intestinal glands,and colonic epithelium.Our results also demonstrated a dramatical increase in AQP3 expression in the colon epithelium of Lepus yarkandensis compared with O.cuniculus.These results revealed that AQPs expression in organs maintaining water balance were a significant difference between the L.yarkandensis and O.cuniculus.Therefore,AQPs played an important role in body water reservation of L.yarkandensis.In summary,AQPs expression in tissues and organs of L.yarkandensis were examined by gene expression profiling chip,immunohistochemistry,qRT-PCR and western blot,and a comparative study with rabbits living in sufficient water sources.It was clear that there was a close relationship between the higher expression levels of AQPs and environmental adaptation of L.yarkandensis.