An Experimental Study on Expression and Localization of Aquaporins in Rat Gastrointestinal Tract.
Grant-in-Aid for Scientific Research (C)
|Research Institution||NIIGATA UNIVERSITY|
SATO Nobuaki Niigata University Medical Hospital, Lecturer Niigata University Hospital, 医学部・附属病院, 講師 (90215822)
YAMAMOTO Tadashi Niigata University School of Medicine, Associate Profess, 医学部, 助教授 (30092737)
親松 学 新潟大学, 医学部附属病院, 医員
小山 諭 新潟大学, 医学部附属病院, 医員
林 光弘 新潟大学, 医学部・附属病院, 医員
HAYASHI Mitsuhiro Niigata University Medial Hospital, Doctor
|Project Fiscal Year
1996 – 1997
Completed(Fiscal Year 1997)
|Budget Amount *help
¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1997 : ¥1,100,000 (Direct Cost : ¥1,100,000)
Fiscal Year 1996 : ¥1,100,000 (Direct Cost : ¥1,100,000)
|Keywords||Aquaporin / gastrointestinal tract / RNase protection assay / pancreas / liver / water channel / 水チャネル / アクアポリン / RN cise protection assay / 消化管 / 脾 / 肝 / 膵 / RNase Protection Assay|
In mammals, a family of water-selective channels, aquaporins (AQPs) has been demonstrated in various organs and tissues including gastrointestinal tract. However, the localization and expression of the AQP family members in the gastrointestinal tract have not entirely elucidated yet.
The aim of this study was to demontrate the expression and distribution of AQPs in rat gastrointestinal tract.
Methods : Expression of AQP 1-5, and AQP 8 was examined by RNase protection assay.Localization of aquaporin1, AQP 3, AQP 4 and AQP 8 was examined by in situ hybridization or by immunohistochemistry.
Results : AQP 1 and AQP 3 were widely distributed through the gastrointenstinal tract from esophagus to colon. In contrast, AQP 4 was selectively expressed in the lower portion of the stomach and the small intestine and AQP 8 in the jejunum and colon.
Conclusion : Several members of AQP family are present separately or overlappingly in rat gastrointestinal tract, and suggesting their roles in t
heabsorption and secretion of water there.
New Aquaporin from Rat Pancreas and Liver
A new water channel (Aquaporin-8, gene symbol AQP8) was isolated from rat pancreas and liver by homology cloning. Ribonuclease protection assay showed intense expression of the gene in the pancreas and the liver, less intense in the colon and the salivary gland and negligible in other organs. The full-length cDNA was obtained by ligation of -1.4 kb cDNA isolated from rat liver cDNA library to -0.5 kb of 5'end fragment obtained by rapid amplification of cDNA ends method.A major transcript of -1.45 kb was demonstrated in the liver and the colon by Northern blot analysis. Expression of AQP8 gene in Xenopus oocytes markedly enhanced osmotic water permeability in a mercury-sensitive manner, indicating a water channel function of this molecule. The open reading frame encoded a 263 amino acid protein with a predicted molecular size of 28 kDa. Hydropathy analysis represented six membranespanning domains and five connecting loops containing two sites of NPA motif as Preserved in other aquaporins. Unlike other mammalian aquaporins, AQP8 has an unusual structure with a long N-terminus and a short C-terminus, which are found in plant aquaporin, r-TIP.By In hybridization, AQP8 mRNA expression was assumed in hepatocytes, acinal cells of pancreas and salivary gland, and absorptive colonic epithelial cells. The physiological role (s) of AQP8 remain to be elucidated. Less
Research Output (3results)