Detection Of Aquaporins Expressed In Small Intestine During ETEC-induced Diarrhea Mice

Aquaporin(AQP)as special water-transporting channels widely expressed at the membrane of eukaryocyte and prokaryocyte.Thirteen homologous members of water channel protein(AQP0-AQP12)have been identified in the animals.They play important roles in transcellular water movement,such as urine concentration,exocrine gland function and metabolism of the eye aqueous humor,brain edema,and cerebrospinal fluid absorption and secretion.The digestive system is capable of bulk fluid transport,quantitatively second only to that of the kidney.It is the frontier areas which involve the expressions and functions of AQPs in the world.The issues of the AQPs in the colon of humans and rats are reported frequently,but a few in the small intestines.In the present study,we identified that the expression of AQP3 in mouse jejunum,but not in duodenum or ileum,AQP4 in mouse ileum,but not in jejunum or duodenum,using reverse transcription PCR(RT-PCR)and Western Blotting.Immunohistochemistry staining showed that AQP3 located in jejunum villi epithelial cells and AQP4 located in intestinal crypt cells.Enterotoxigenic Escherichia coli(ETEC)is the leading cause of bacteria diarrhea in humans and farming animals worldwide.The most accepted mechanism is that ETEC localizes in the small intestine easily and secretes enterotoxin(LT and ST)to cells,resulting in the secretion of excessive amount of fluid.The excessive loss of water in ETEC-induced diarrhea was secreted by the action of transport proteins in the lumen,such as cystic fibrosis transmembrane regulator(CFTR).However,it is unknown that ETEC influence water transports in intestinal epithelial cells.Using ETEC-induced diarrhea mice model,we demonstrated that the levels of mRNA expression and protein concentration of AQP3 in jejunum and AQP4 in ileum were significantly decreased gradually in continuous 7 days compared to control by qPCR and ELISA.There results suggested that impairment water influx also play an important role in ETEC-induced diarrhea.