摘要
水通道蛋白(Aquaporin,AQP)是广泛存在于细胞膜上转运水的特异性孔道。大量研究表明,水通道蛋白在许多体液转运的生理及病理过程包括尿浓缩、外分泌腺功能、眼球房水代谢、脑脊液分泌和吸收以及脑水肿形成中发挥重要作用。近期的一些研究显示水通道蛋白还参与细胞的一些重要生命活动包括细胞增殖、迁移和凋亡等。
肝胆系统的主要生理功能不仅是生成胆汁,而且还可以修饰和浓缩胆汁。正常情况下胆汁中含有98%以上的水。如何保证高效的水的转运,对于维持肝胆系统的正常生理功能是十分重要的。目前已知在肝胆系统中有7种水通道表达:AQP0,AQP1,AQP4,AQP5,AQP8,AQP9,AQP11,其分布遍及肝细胞、胆管上皮细胞、胆囊上皮细胞和血管内皮细胞。AQP0主要表达于肝细胞中央静脉周围区域;AQP1广泛存在肝脏血管内皮细胞、胆管上皮细胞和胆囊上皮细胞;AQP8分别在肝细胞毛细胆管膜和胆囊上皮细胞表达;AQP9主要集中在肝细胞的窦基底膜。肝胆系统中广泛分布着水通道蛋白AQPs,但到目前为止,究竟诸多AQPs在胆汁形成、修饰及浓缩过程中起到什么样的作用?一些研究仍然处在间接的、推测水平。
本课题利用AQP8和AQP1基因敲除小鼠模型,系统地研究了水通道蛋白AQP8和AQP1在小鼠“原始”胆汁的形成和胆囊内胆汁浓缩过程中的作用。我们首先引取了小鼠的生理水平下的胆汁。与野生型小鼠相比,AQP8基因敲除小鼠的胆汁分泌量明显减少。为了避免胆管对胆汁形成修饰作用,我们使用胆盐刺激小鼠,加快胆汁分泌的速度,结果仍显示,AQP8基因敲除小鼠的胆汁分泌量明显少于野生型小鼠。胆汁成分分析,基础状态下的两组小鼠的胆汁无明显差异,但是胆盐刺激后,AQP8基因敲除小鼠胆汁内的总胆汁酸与谷胱甘肽的含量明显高于野生型小鼠的,表明水通道蛋白AQP8参与了胆汁的形成过程。为了更进一步确定AQP8在“原始”胆汁形成中的作用,本课题组进行了细胞水平的实验研究,分离了肝细胞对(Couplets),发现两组小鼠的肝细胞数量及形态无差异,以及肝细胞对在肝细胞中的比例也无不同。利用荧光染料可被肝细胞分泌进入毛细胆管的原理,分析了肝细胞的胆汁分泌情况,荧光结果显示,与野生型小鼠的肝细胞对比较,在AQP8基因敲除小鼠的肝细胞对中,有很少的胆汁被分泌进入毛细胆管。
另外,胆囊可以重吸收肝胆汁中的大量水分,在食物消化时,胆囊收缩,将浓缩的胆汁排入十二指肠以助于食物的消化和吸收,提示胆囊上存在着高效转运水的水通道蛋白AQPs。从形态学上观察,两组小鼠的胆囊结构无明显差异。但通过RT-PCR、Real-time PCR和免疫荧光分析发现水通道蛋白AQP1在野生型小鼠的胆囊上皮细胞上高表达,本研究首次利用calcein荧光技术测量小鼠胆囊的跨上皮水转运,结果发现,AQP1基因敲除小鼠的胆囊跨上皮水转运速度明显慢于野生型小鼠,提示AQP1是胆囊水转运的主要途径。而且野生型小鼠胆囊的跨上皮水转运速度是目前已知哺乳动物中跨上皮水转运速度最快的。此外,利用本实验室可以做显微手术的优势,将小鼠的胆囊里层外翻,结合荧光染料calcein-AM,测量胆囊上皮细胞顶质膜的水通透性。分析结果显示,与野生型小鼠相比,AQP1基因敲除小鼠的胆囊上皮细胞顶质膜的水通透性显著降低。根据结果我们估计,胆囊上皮细胞膜上存在约4000 /um2个AQP1,占20%质膜蛋白。由此可见,胆囊上皮的水转运是跨细胞转运,而不是细胞旁转运。但胆囊胆汁成分分析表示,两组小鼠的胆汁成分含量基本相似。表明在胆囊胆汁浓缩过程中还存在其他的机制,需进一步研究。
综上所述,水通道蛋白AQP8表达定位于肝脏并在肝胆汁形成过程中发挥了重要的作用,水通道蛋白AQP1介导了胆囊上皮细胞膜的高水通透性,但在胆囊胆汁浓缩中并无重要作用。
Members of the AQP family are distributed in many cell types in different organ systems where they play important roles in various physiological functions and pathological conditions including urinary concentrating function, exocrine glandular fluid secretion, brain edema formation, regulation of intracranial and intraocular pressure, skin hydration, fat metabolism, tumor angiogenesis,cell migration and apoptosis.
The major function of hepatobiliary system includes bile formation and modification by secretory and absorptive processes in the epithelial cells of intrahepatic bile ducts and gallbladder. Aquaporin (AQP)-mediated transepithelial water transport mechanism may play an important role in bile formation. To date, 13 AQPs have been found in mammals, with many numbers (AQP0, AQP1, AQP4, AQP5, AQP8, AQP9, AQP11) being localized to the hepatobiliary system in the plasma membranes of hepatocytes, the epithelial cell of bile ducts , the epithelial cells of gallbladder and intrahepatic vascular endothelial cells. In the present study, we focus on the expression and potential physiological roles of AQP1 and AQP8 in bile secretion and concentration.
We collected bile from wild type and AQP8 null mice. Compare with wild type mice, bile flow was significantly decreased in AQP8 null mice under both basal and bile salt-stimulated conditions. Bile composition analysis showed no difference in the total bile acid and glutathione concemtration under physiological condition between wild type and AQP8 null mice. But after bile salt stimulation, total bile acid and glutathione concentration in bile were significantly increased in AQP8 null mice compared with wild type mice. Those data indicated that AQP8-facilitated canalicular membrane water transport is involved in hepatic bile secretion.
To further confirm the reduced hepatic bile secretion in AQP8-/- liver, we isolated hepatocyte couplets from wild type and AQP8 null mice. Although the couplets number and morphology are similar in both genotypes, fluorescence assay showed significantly decreased bile secretion into canalicular space of hepatocyte couplets in AQP8 null mice compare with wild type mice. These results provide direct evidence that AQP8-mediated water transport playa an important role in hepatic bile secretion.
Water transport across gallbladder epithelium is driven by osmotic gradients generated from active salt absorption and secretion. Aquaporin (AQP) water channels have been proposed to facilitate transepithelial water transport in gallbladder and to modulate bile composition. We found strong AQP1 immunofluorescence at the apical membrane of mouse gallbladder epithelium.Transepithelial osmotic water permeability (Pf) was measured in freshly isolated gallbladder sacs from the kinetics of luminal calcein self-quenching in response to an osmotic gradient. Pf was very high (0.12 cm/s) in gallbladders from wildtype mice, cAMP-independent, and independent of osmotic gradient size and direction. Although gallbladders from AQP1 knockout mice had similar size and morphology to those from wildtype mice, their Pf was reduced by ~10-fold. Apical plasma membrane water permeability was greatly reduced in AQP1-deficient gallbladders, as measured by cytoplasmic calcein quenching in perfluorocarbon-filled, inverted gallbladder sacs. However, neither bile osmolality nor bile salt concentration differed in gallbladders from wildtype vs. AQP1 knockout mice. Our data indicate constitutively high water permeability in mouse gallbladder epithelium involving transcellular water transport through AQP1. The similar bile salt concentration in gallbladders from AQP1 knockout mice argues against a physiologically important role for AQP1 in mouse gallbladder.
In conclusion, our results provide evidence for AQP8-mediated water transport across hepatocyte canalicular membrane plays an important role in hepatic bile secretion. AQP1 creates high osmotic water permeability in mouse gallbladder epithelium, but does not affect bile concentration.
引文
[1] Jones AL, Schmucker DL, Renston RH, et al.The architecture of bile secretion. A morphological perspective of physiology[J]. Dig Dis Sci,1980,25(1): 609-629.
[2] Hagenbuch B, Meier PJ. The superfamily of organic anion transporting polypeptides[J]. Biochim Biophys Acta,2003,1609(17): 1-18.
[3] Meier PJ, Stieger B. Bile salt transporters[J]. Annu Rev Physiol,2002,64(2): 635-661.
[4] Trauner M, Boyer JL. Bile salt transporters: molecular characterization, function, and regulation[J]. Physiol Rev,2003,83(3): 633-671.
[5] Wakabayashi Y, Lippincott-Schwartz J, Arias IM. Intracellular trafficking of bile salt export pump (ABCB11) in polarized hepatic cells: constitutive cycling between the canalicular membrane and rab11-positive endosomes[J]. Mol Biol Cell,2004,15(1): 3485-3496.
[6] Kipp H, Arias IM. Trafficking of canalicular ABC transporters in hepatocytes[J]. Annu Rev Physiol, 2002, 64(3): 595-608.
[7] Rappaport AM. The microcirculatory acinar concept of normal and pathological hepatic structure[J]. Beitr Pathol, 1976, 157(8): 215-243.
[8] Gonzalez J, Esteller A. Heterogeneity of rabbit hepatocytes for bile secretion after acinar zone 3 damage induced by bromobenzene. Effect of bilirubin and bile salt infusions[J]. Biochem Pharmacol, 1985, 34 (1): 507-514.
[9] Katz NR. Metabolic heterogeneity of hepatocytes across the liver acinus[J]. J Nutr, 1992,122(7): 843-849.
[10] Inoue M, Kinne R, Tran T, Arias IM. The mechanism of biliary secretion of reduced glutathione. Analysis of transport process in isolated rat-liver canalicular membrane vesicles[J]. Eur J Biochem, 1983, 134(8): 467-471.
[11] Erlinger S. Bile flow. In: Arias IM, Popper H, Jacoby WB, Schachter D, et al.The Liver: Biology and Pathobiology[M]. New York: Raven Press,1988: 643-664.
[12] Quintao E, Grundy SM, Ahrens EH Jr. Effects of dietary cholesterol on the regulation of total body cholesterol in man[J]. J Lipid Res,1971,12(1): 233-247.
[13] Erlinger S, Dhumeaux D, Berthelot P, Dumont M. Effect of inhibitors of sodium transport on bile formation in the rabbit[J]. Am J Physiol,1970,219(13): 416-422.
[14] Zsembery A, Thalhammer T, Graf J. Bile Formation: a Concerted Action of Membrane Transporters in Hepatocytes and Cholangiocytes[J]. News Physiol Sci,2000,15(1): 6-11.
[15] Boyer JL, Klatskin G. Canalicular bile flow and bile secretory pressure. Evidence for a non-bile salt dependent fraction in the isolated perfused rat liver[J]. Gastroenterology, 1970, 59(1): 853-859.
[16] Erlinger S. Does Na+-K+-ATPase have any role in bile secretion[J] Am J Physiol, 1982,243(14): G243-G247.
[17] Wheeler HO, Ross ED, Bradley SE. Canalicular bile production in dogs[J]. Am J Physiol, 1968, 214(9): 866-874.
[18] Boyer JL. Canalicular bile formation in the isolated perfused rat liver[J]. Am J Physiol, 1971, 221(12): 1156-1163.
[19] Nathanson MH, Boyer JL. Mechanisms and regulation of bile secretion[J]. Hepatology, 1991, 14(1): 551-566.
[20] Tavoloni N. The intrahepatic biliary epithelium: an area of growing interest in Hepatology [J]. Semin Liver Dis, 1987, 7(1):280-292.
[21] Meier PJ, Stieger B. Bile salt transporters [J]. Annu Rev Physiol, 2002, 64(2): 635-661.
[22] Arrese M, Ananthananarayanan M, Suchy FJ. Hepatobiliary transport: molecular mechanisms of development and cholestasis[J]. Pediatr Res, 1998, 44(1): 141-147.
[23] Hagenbuch B, Meier PJ. Molecular cloning, chromosomal localization, and functional characterization of a human liver Na+/bile acid cotransporter[J]. J Clin Invest, 1994, 93(2):1326-1331.
[24] Meier PJ, Eckhardt U, Schroeder A, et al.Substrate specificity of sinusoidal bile acid and organic anion uptake systems in rat and human liver[J]. Hepatology, 1997, 26(1): 1667-1677.
[25] Kullak-Ublick GA, Hagenbuch B, Stieger B, et al.Molecular and functional characterization of an organic anion transporting polypeptide cloned from human liver[J]. Gastroenterology, 1995, 109(9): 1274-1282.
[26] Ballatori N. Biology of a novel organic solute and steroid transporter, OSTalpha-OSTbeta[J]. Exp Biol Med (Maywood), 2005, 230(10): 689-698.
[27] Kaplowitz N. Physiological significance of glutathione S-transferases[J]. Am J Physiol, 1980,239(12): G439-G444.
[28] Crawford JM, Berken CA, Gollan JL. Role of the hepatocyte microtubular system in the excretion of bile salts and biliary lipid: implications for intracellular vesicular transport[J]. J Lipid Res, 1988, 29(1): 144-156.
[29] Lamri Y, Roda A, Dumont M, Feldmann G, Erlinger S. Immunoperoxidase localization of bile salts in rat liver cells. Evidence for a role of the Golgi apparatus in bile salt transport[J]. J Clin Invest, 1988, 82(3): 1173-1182.
[30] Crawford JM, Vinter DW, Gollan JL. Taurocholate induces pericanalicular localization of C6-NBD-ceramide in isolated hepatocyte couplets[J]. Am J Physiol, 1991, 260(9): G119-G132.
[31] Dubin M, Maurice M, Feldmann G, Erlinger S. Influence of colchicine and phalloidin on bile secretion and hepatic ultrastructure in the rat. Possible interaction between microtubules and microfilaments[J]. Gastroenterology, 1980, 79(5):646-654.
[32] Trauner M, Meier PJ, Boyer JL. Molecular pathogenesis of cholestasis[J]. N Engl J Med, 1998, 339(19): 1217-1227.
[33] Kipp H, Pichetshote N, Arias IM. Transporters on demand: intrahepatic pools of canalicular ATP binding cassette transporters in rat liver[J]. J Biol Chem, 2001,276 (13): 7218-7224.
[34] Gerloff T, Stieger B, Hagenbuch B, Madon J, Landmann L,Roth J, Hofmann AF, Meier PJ. The sister of P-glycoprotein represents the canalicular bile salt export pump of mammalian liver[J]. J Biol Chem, 1998, 273(13): 10046-10050.
[35] Gatmaitan ZC, Nies AT, Arias IM. Regulation and translocation of ATP-dependent apical membrane proteins in rat liver[J]. Am J Physiol,199,272(11): G1041-G1049.
[36] Strautnieks SS, Bull LN, Knisely AS, Kocoshis SA, et al. A gene encoding a liver-specific ABC transporter is mutated in progressive familial intrahepatic cholestasis[J]. Nat Genet,1998,20(1): 233-238.
[37] Aza MJ, Gonzalez J, Esteller A. Effect of diethyl maleate pretreatment on biliary excretion and choleretic action of sulfobromophthalein in rats[J]. Arch Int Pharmacodyn Ther,1986,281(9): 321-330.
[38] Garcia-Marin JJ, Villanueva GR, Esteller A. Diabetesinduced cholestasis in the rat: possible role of hyperglycemia and hypoinsulinemia[J]. Hepatology,1988,8(1): 332-340.
[39] Meier PJ, Knickelbein R, Moseley RH, et al.Evidence for carrier-mediated chloride/bicarbonate exchange in canalicular rat liver plasma membrane vesicles[J]. J Clin Invest,1985,75(8): 1256-1263.
[40] Paulusma CC, Bosma PJ, Zaman GJ, et al.Congenitaljaundice in rats with a mutation in a multidrug resistance-associated protein gene[J]. Science, 1996,271(13):1126-1128.
[41] Inoue M, Kinne R, Tran T, Arias IM. The mechanism of biliary secretion of reduced glutathione. Analysis of transport process in isolated rat-liver canalicular membrane vesicles[J]. Eur J Biochem,1983,134(7): 467-471.
[42] Paulusma CC, van Geer MA, Evers R, Heijn M, et al.Canalicular multispecific organic anion transporter/multidrug resistance protein 2 mediates low-affinity transport of reduced glutathione[J]. J Biochem,1999,338(12): 393-401.
[43] Martinez-Anso E, Castillo JE, Diez J, et al.Immunohistochemical detection of chloride/bicarbonate anion exchangers in human liver[J]. Hepatology,1994,19(2):1400-1406.
[44] Fitz JG, Persico M, Scharschmidt BF. Electrophysiological evidence for Na+-coupled bicarbonate transport in cultured rat hepatocytes[J]. Am J Physiol,1989,256(9): G491-G500.
[45] Renner EL, Lake JR, Scharschmidt BF, et al . Rat hepatocytes exhibit basolateral Na+/HCO3-cotransport[J]. J Clin Invest,1989,83(4): 1225-1235.
[46] Benedetti A, Strazzabosco M, Ng OC, Boyer JL. Regulation of activity and apical targeting of the Cl-/HCO3- exchanger in rat hepatocytes[J]. Proc Natl Acad Sci, 1994, 91(7): 792-796.
[47] Gradilone SA, Garcia F, Huebert RC, et al. Glucagon induces the plasma membrane insertion of functional aquaporin-8 water channels in isolated rat hepatocytes[J].Hepatology, 2003,37(3): 1435-1441.
[48]Scharschmidt BF, Van Dyke RW. Mechanisms of hepatic electrolyte transport[J].Gastroenterology,1983,85(4): 1199-1214.
[49] Meier PJ, Steiger B. Molecular mechanisms in bile formation[J]. NewsPhysiol Sci,2000, 15(1): 89-93.
[50] Marinelli RA, LaRusso NF. Solute and water transport pathways in cholangiocytes[J]. Semin Liver Dis,1996,16(3): 221-229.
[51] Masyuk AI, Marinelli RA, LaRusso NF. Water transport by epithelia of the digestive tract[J]. Gastroenterology,2002,122(4): 545-62.
[52]Agre P.Aquaporin water channels[R]. Biosci Rep,2004,24:127–63.
[53] Denker BM,Smith BL,Kuhajda FP,Agre P. Identification, purification, and partial characterization of a novel Mr 28,000 integral membrane protein from erythrocytes and renal tubules[J]. J Biol Chem, 1988, 263(8):15634-42.
[54] Preston GM, Carroll TP, Guggino WB, Agre P. Appearance of water channels in Xenopus oocytes expressing red cell CHIP28 Protein [J]. Science, 1992, 256(7):385-87.
[55] Itoh T, Rai T, KuwaharaM, et al. Identification of a novel aquaporin, AQP12, expressed in pancreatic acinar cells [J]. Biochem Biolphys Res Commun, 2005, 330 (8): 832–838.
[56] King L S, Kozono D, Agre P. From structure to disease: the evolving tale of aquaporin biology [J]. Nat Rev Mol Cell Biol, 2004, 5(9):687-698.
[57] Morishita Y, Matsuzaki T, Hara-chikuma M, et al. Disruption of aquaporin-11 produces polycystic kidneys following vacuolization of the proximal tubule [J]. Mol Cell Biol, 2005, 25(17): 7770-7779.
[58] Agre P, Preston GM, Smith BL, Jung JS, Raina S, Moon C, Guggino WB, et al. Aquaporin CHIP: the archetypal molecular water channel [J]. Am J Physiol, 1993, 265(1): F463-76.
[59] Agre P. Membrane water transport and aquaporins: looking back [J]. Biol Cell, 2005, 97(6):355-6.
[60] Kozono D, Masato Y, King LS, et al.Aquaporin water channels: atomic structure and molecular dynamics meet clinical medicine [J]. J Clin Invest, 2002, 109(4):1395-9.
[61] Heymann JB, Engel A. Aquaporins: phylogeny, structure, and physiology of water channels[J]. News Physiol Sci,1999,14(4): 187-193.
[62] Murata K, Mit suoka K, Hirai T, et al. Structural determinants of water permeation through aquaporin-1 [J]. Nature,2000,407(1):5992605.
[63] Kozono D, Masato Y, King LS, et al.Aquaporin water channels: atomic structure and molecular dynamics meet clinical medicine. [J] J Clin Invest, 2002,109(1): 1395-99.
[64] Preston GM, Jung JS, Guggino WB, et al. The mercury-sensitive residue at cysteine 189 in the CHIP28 water channel [J]. J Biol Chem,1993,268(4): 17-20.
[65] Hasegawa H, Ma T, Skach W, et al.. Molecular cloning of a mercurial-insensitive water channel expressed in selected water-transporting tissues[J]. J Biol Chem,1994,269(1): 5497-00.
[66] Jung JS, Bhat RV, Preston GM, et al. Molecular characterization of an aquaporin cDNA from brain: candidate osmoreceptor and regulator of water balance [J]. Proc Natl Acad Sci,1994,91(1): 13052-56.
[67] Burghardt B, Elkaer M L, Kwon T H, et al. Distribution of aquaporin water channels AQP1 and AQP5in the ductal system of the human pancreas[J]. J Gut, 2003, 52(7): 1008-1016.
[68] Gresz V, Kwon T H, Hurley P T, et al. Identification and localization of aquaporin water channels in human salivary glands [J]. Am J Physiol Gastrointest Liver Physiol, 2001, 281(1): G247-254.
[69] Elkjaer M L, Nejsum L N, Gresz V, et al. Immunolocalization of aquaporin-8 in rat kidney,gastrointestinal tract, testis, and airways[J]. Am J Physiol Renal Physiol, 2001, 281(6): F1047-1057.
[70] Nejsum L N, Elkjaer M, Hager H, et al. Localization of aquaporin-7 in rat and mouse kidney using RT-PCR, immunoblotting, and immunocytochemistry[J]. Biochem Biophys Res Commun, 2000, 277(1):164-170.
[71] Li J, Kuang K, Nielsen S, et al. Molecular identification and immunolocalization of the water channel protein aquaporin 1 in CBCECs [J]. Invest Ophthalmol Vis Sci, 1999, 40(6): 1288-1292.
[72] Kim I B, Oh S J, Nielsen S, et al. Immunocytochemical localization of aquaporin 1 in herat retina[J]. Neurosci Lett, 1998, 244(1): 52-54.
[73] Zhong S X, Liu Z H. Expression of aquaporins in the cochlea and endolymphatic sac of guinea pig [J]. ORL J Otorhinolaryngol Relat Spec, 2003, 65(5): 284-289.
[74] Terris J, Ecelbarger C A, Marples D, et al. Distribution of aquaporin-4 water channel expression within rat kidney [J]. Am J Physiol Renal Physiol, 1995, 26(9): 775–785.
[75] Pedro Gallardo, Nancy Olea, Francisco V. Sepúlveda. Distribution of aquaporins in the colon of Octodon degus, a South American desert rodent[J]. Am J Physiol Regulatory Integrative Comp Physiol, 2002, 283(3): 779–788.
[76] Grazia P. Nicchia, Antonio Frigeri, Beatrice Nico, et al. Tissue Distribution and Membrane Localization of Aquaporin-9 Water Channel: Evidence for Sex-linked Differences in Live [J]. J Histochem Cytochem, 2001, 49(12): 1547-1556.
[77] Effros R M, Darin C, Jacobs E R, et al. Water transport and the distribution of aquaporin-1 in pulmonary air spaces[J]. J Appl Physiol, 1997, 83(3): 1002-1016.
[78] Schey K L, Ball L E, Crouch R K, et al. The Distribution of Phosphorylated and Posttranslationally Modified Aquaporin 0 Within the Normal Human Lens[J]. Invest Ophthalmol Vis Sci, 2003, 4(4): 4483-85.
[79] Nielsen S, King L S., Christensen B M, et al. Aquaporins in complex tissues. II. Subcellular distribution in respiratory and glandular tissues of rat [J]. Am J Physiol Cell Physiol, 1997, 27(3): 1549-1561.
[80] Steffen Hamann, Thomas Zeuthen, Morten La Cour, et al. Aquaporins in complex tissues: distribution of aquaporins 1-5 in human and rat eye [J]. Am J Physiol Cell Physiol, 1998, 27(4): 1332-1345.
[81] Kishore B K, Terris J M, Knepper M A. Quantitation of aquaporin-2 abundance in microdissected collecting ducts: axial distribution and control by AVP [J]. Am J Physiol Renal Physiol, 1996,27(1): 62-70.
[82] Johannes Loffing, Dominique Loffing-Cueni, Andreas Macher, et al. Localization of epithelial sodiumchannel and aquaporin-2 in rabbit kidney cortex[J]. Am J Physiol Renal Physiol,2000,27(8): 530-539.
[83] Mandon B, Nielsen S, Kishore B K, et al. Expression of syntaxins in rat kidney[J]. Am J Physiol, 1997, 273(5 Pt 2): F718-730.
[84] Calamita G, Mazzone A, Cho Y S,et al. Expression and Localization of the Aquaporin-8 Water Channel in Rat Testis[J]. Biol Reprod,2001,64(3): 1660-1666.
[85] Pastor Soler N, Bagnis C, Sabolic I, et al. Aquaporin 9 Expression along the Male Reproductive [J] Tract Biol Reprod, 2001, 65(3): 384-393.
[86] Funaki H, Yamamoto T, Koyama Y,et al. Localization and expression of AQP5 in cornea,serous salivary glands, and pulmonary epithelial cells [J]. Am J Physiol Cell Physiol, 1998, 275(15): 1151-1157.
[87] Morishita Y, Sakube Y, Sasaki S, et al. Molecular mechanisms and drug development in aquaporin water channel diseases: aquaporin superfamily (superaquaporins): expansion of aquaporins restricted to multicellular organisms [J]. J Pharmacol Sci, 2004,96(3): 276-279.
[88] Verbalis J G, Murase T, Ecelbarger C A, et al. Studies of renal aquaporin-2 expression during renal escape from vasopressin-induced antidiuresis[J]. Adv Exp Med Biol, 1998, 449(17): 395-406.
[89] Christensen B M, Zelenina M, Aperia A, et al. Localization and regulation of PKA-phosphorylated AQP2 in response to V(2)-receptor agonist/antagonist treatment[J]. Am J Physiol Renal Physiol, 2000, 278(1): F29-42.
[90] Katsura T, Verbavatz J, Farinas J, et al. Constitutive And Regulated Membrane Expression of aquaporin-1 and aquaporin-2 water channels in stably transfected Llc-pk1 epithelial-cells [J]. Proc Natl Acad Sci, 1995, 92(16): 7212-7216.
[91] Hayashi, M, Sasaki S, Tsuganezawa H, et al. Expression and distribution of aquaporin of collecting duct are regulated by vasopressin V2 receptor in rat kidney [J]. J Clin Invest, 1994, 94(8): 1778-1783.
[92] Matsumura Y, Uchida S, Rai T, et al. Transcriptional regulation of aquaporin-2 water channel gene by cAMP [J]. J Am Soc Nephrol,1997, 8(1): 861-867.
[93] Huebert RC, Splinter PL, García F, Marinelli RA, LaRusso NF. Expression and localization of aquaporin water channels in rat hepatocytes.evidence for a role in canalicular bile secretion[J]. J Biol Chem, 2002,277(16): 22710-17.
[94] Garcia F, Kierbel A, Larocca MC, Gradilone SA, Splinter P, LaRusso NF, Marinelli RA. The water channel aquaporin-8 is mainly intracellular in rat hepatocytes and its plasma membrane insertion is stimulated by cyclic AMP[J]. J Biol Chem,2001,276(17): 12147-52.
[95] Calamita G, Mazzone A, Bizzoca A, Cavalier A, Cassano G, Thomas D, Svelto M. Expression and immunolocalization of the aquaporin-8 water channel in rat gastrointestinal tract [J]. Eur J Cell Biol,2001,80(6): 711-19.
[96] Elkjaer ML, Nejsum LN, Gresz V, Kwon TH, Jensen UB, Frokiaer J, Nielsen S. Immunolocalizationof aquaporin-8 in rat kidney, gastrointestinal tract, testis, and airways[J]. Am J Physiol, 2001,281(8): F1047-57.
[97] Tani T, Koyama Y, Nihei K, Hatakeyama S, Ohshiro K, Yoshida Y, Yaoita E, et al. Immunolocalization of aquaporin-8 in rat digestive organs and testis[J]. Arch Histol Cytol, 2001,64(12): 159-68.
[98] Elkjaer M-L, Vajda Z, Nejsum LN, Kwon T-H, Jensen UB, Amiry- Moghaddam M, Frokiaer J, et al. Immunolocalization of AQP9 in liver, epididymis, testis, spleen, and brain[J]. Biochem Biophys Res Commun, 2000,276(4):1118-28.
[99] Nicchia GP, Frigeri A, Nico B, Ribatti D, Svelto M. Tissue distribution and membrane localization of aquaporin-9 water channel: evidence for sex-linked differences in liver[J]. J Histochem Cytochem, 2001,49(1):1547-56.
[100] Morishita Y, Matsuzaki T, Hara-chikuma M, Andoo A, Shimono M, Matsuki A, et al. Disruption of aquaporin-11 produces polycystic kidneys following vacuolization of the proximal tubule [J]. Mol Cell Biol, 2005,25(1):7770-7779.
[101] Carreras FI, Gradilone SA, Mazzone A, García F, Huang BQ, Ochoa JE, Tietz P, et al. Rat hepatocyte aquaporin-8 water channels are down-regulated in extrahepatic cholestasis[J]. Hepatology, 2003,37(4):1026-33.
[102] Ferri D, Mazzone A, Liquori GE, et al. Ontogeny, distribution, and possible functional implications of an unusual aquaporin, AQP8, in mouse liver[J]. Hepatology, 2003,38(4): 947-57.
[103] Elkjaer ML, Nejsum LN, Gresz V, et al. Immunolocalization of aquaporin-8 in rat kidney, gastrointestinal tract, testis, and airways[J]. Am J Physiol Renal Physiol, 2001,281(12):F1047–F1057.
[104] Mazzone A, Tietz P, J efferson J, et al. Isolation and characterization of lipid microdomains f rom apical and basolateral plasma membranes of rat hepatocytes[J]. Hepatology, 2006, 43 (2):2872296.
[105] Portincasa P , Moschetta A , Mazzone A , et al . Water handling and aquaporins in bile formation: recent advances and research trends [J]. J Hepatol, 2003, 39(5):8642874.
[106] Gradilone SA, Garcia F, Huebert RC, et al. Glucagon induces the plasma membrane insertion of functional aquaporin-8 water channels in isolated rat hepatocytes [J]. Hepatology, 2003,37(3): 1435-41.
[107] Ishibashi K, Kuwahara M, Kageyama Y, et al.Cloning and functional expression of a second new aquaporin abundantly expressed in testis. [J]Biochem Biophys Res Commun, 1997, 237(14): 714-18.
[108] Ferri D, Mazzone A, Liquori GE, Cassano G, Svelto M, Calamita G. Ontogeny, distribution, and possible functional implications of an unusual aquaporin, AQP8, in mouse liver[J]. Hepatology, 2003,38(2): 947-57.
[109] Portincasa P, Moschetta A, Mazzone A, et al. Water handing and aquaporins in bile formation: recent advances and research trends [R]. J Hepatol, 2003, 39(3): 864 - 874.
[110] Calamita G, Ferri D, Gena P, et al. The inner mitochondrial membrane has aquaporin8 water channels and is highly permeable to water [J]. J Biol Chem, 2005, 280(13): 17149 - 17153.
[111] Lee WK, Thévenod F. A role for mitochondrial aquaporins in cellular life-and-death decisions[J]. Am J Physiol Cell Physiol, 2006, 29(2):C1952202.
[112] Elkjaer M-L, Vajda Z, Nejsum LN, et al. Immunolocalization of AQP9 in liver, epididymis, testis, spleen, and brain[J]. Biochem Biophys Res Commun, 2000, 276(2): 1118-28.
[113] Nicchia GP, Frigeri A, Nico B, et al. Tissue distribution and membrane localization of aquaporin-9 water channel; evidence for sex linked differences in liver [J]. J Histochem Cytochem, 2001, 493(13):1547 - 1556.
[114] Carbrey JM, Gorelick-Feldman DA, Kozono D, et al. Aquaglyceroporin AQP9: solute permeation and metabolic control of exp ression in liver [J]. Proc Natl Acad Sci, 2003, 100(11): 2945 - 2950.
[115] Kuriyama H, Shimomura I, Kishida K, et al. Coordinated regulation of fat-specific and liver-specific glycerol channels, aquaporin adipose and aquaporin-9[J]. Diabetes, 2002,51(6): 2915-21.
[116] Rojek AM , Skowronski MT , Füchtbauer EM , et al . Defective glycerol metabolism in aquaporin 9 (AQP9) knockout mice[J]. Proc N at l A cad Sci, 2007, 104(9): 3609-3614.
[117] Patsouris D, Mandard S, Voshol PJ, et al. PPARalpha governs glycerol metabolism [J]. J Clin Invest, 2004,114(5):94–103.
[118] Hibuse T, Maeda N, Nagasawa A, et al.Aquaporins and glycerol metabolism[J]. Biochim Biophys Acta, 2006,1758(14):1004–11.
[119] Rodríguez A, Catalán V, Gómez-Ambrosi J, et al. Role of aquaporin-7 in the pathophysiological control of fat accumulation in mice[J]. FEB S L ett, 2006,580 (20): 477124776.
[120] Takata K, Matsuzaki T, Tajika Y. Aquaporins: water channel proteins of the cell membrane[J]. Prog Histochem Cytochem, 2004,39(4):1-83.
[121] Gonen T, Sliz P, Kistler J, et al.Aquaporin-0 membrane junctions reveal the structure of a closed water pore [J]. Nature, 2004,429(20):193–7.
[122] Gorelick DA, Praetorius J, Tsunenari T, et al. Aquaporin-11: a channel protein lacking apparent transport function expressed in brain [J]. BMC Biochem,2006,7(1):14.
[123] Yakata K, Hiroaki Y, Ishibashi K, et al. Aquaporin-11 containing a divergent NPA motif has normal water channel activity[J]. Biochim Biophys Acta,2007,1768(21):688–93.
[124] Masyuk AI, Marinelli RA, LaRusso NF. Water transport by epithelia of the digestive tract[J]. Gastroenterology,2002,122(9):545-562.
[125] Masyuk AI, LaRusso NF. Aquaporin-mediated water transport in intrahepatic bile duct epithelial cells. In: Alpini G, Alvaro D, Marzioni M, LeSage G, LaRusso N, eds. The Pathobiology of the Biliary Epitheloia[J].Georgetown,TX:Eurekah.com, 2004,277(9):127-135.
[126] Marinelli RA, Tietz PS, Pham LD, et al. Secretin induces the apical insertion of aquaporin-1 water channels in rat cholangiocytes[J]. Am J Physiol, 1999, 276(12): G280 - G286.
[127] Marinelli RA, Pham LD, Tietz PS, et al. Expression of aquaporin-4 water channels in ratcholangiocytes[J]. Hepatology, 2000, 31(2): 1313-1317.
[128] Splinter PL, Masyuk A I, LaRusso NF. Specific inhibition of AQP1 water channels in isolated rat intrahepatic bile duct units by small interfering RNAs[J]. J Biol Chem, 2003, 278(7): 6268 - 6274.
[129] Splinter PL, Masyuk A I, Marinelli RA, et al. AQP4 transfected into mouse cholangiocytes promotes water transport in biliary epithelia[J]. Hepatology, 2004, 39(1): 109 - 116.
[130] Tietz PS, Marinelli RA, Chem XM, et al. Agonist-induced coordinated trafficking of functionally related transport proteins forwater and ions in changiocytes[J]. J Biol Chem, 2003, 278(20): 20413 - 20419.
[131] Masyuk AI, Masyuk TV, Tietz P S, et al. Intrahepatic bile ducts transport water in response to absorbed glucose [J]. Am J Physiol Cell Physiol, 2002 ,283(12) :C7852-C7859.
[132] Ma T, Jayaraman S, Wang KS, et al. Defective dietary fat processing in transgenic mice lacking aquaporin-1 water channels[J]. Am J Physiol Cell Physiol, 2001, 280(3): C126 - C134.
[133] Calamita G, Ferri D, Bazzini C, et al. Expression and subcellular localization of the AQP8 and AQP1 water channels in the mouse gall-bladder epithelium[J]. Biol Cell, 2005,97(4): 415-423.
[134] Sui H, Han B-G, Lee JK, Walian P, Jap BK. Structural basis of water specific transport through the AQP1 water channel[J]. Nature, 2001, 414(14):872-878.
[135] Jablonski EM , Mattocks MA , Sokolov E , et al . Decreased aquaporin expression leads to increased resistance to apoptosis in hepatocellular carcinoma[J]. Cancer L ett, 2007, 250 (1): 622-631.
[136] Tietz P, Jefferson J, Pagano R, Larusso NF. Membrane microdomains in hepatocytes: potential target areas for proteins involved in canalicular bile secretion [J]. J Lipid Res,2005, 46(7):1426-32.
[137] Marinelli RA, Pham L, Agre P, LaRusso NF. Secretin promotes osmotic water transport in rat cholangiocytes by increasing aquaporin-1 water channels in plasma membrane. Evidence for a secretin-induced vesicular translocation of aquaporin-1[J]. J Biol Chem, 1997, 272(21): 12984-12988.
[138] Yang, B, Song, Y, Zhao, D, Verkman, AS. Phenotype analysis of aquaporin-8 null mice[J]. Am J Physiol, 2005, 288(13): C1161-C1170.
[139] Suzuki K, Kottra G, Kampmann L, Fromter, E. Square wave pulse analysis of cellular and paracellular conductance pathways in Necturus gallbladder epithelium[J]. Pftugers Arch, 1982,394(5): 302-312.
[140] Cotton CU, Weinstein AM, Reuss L. Osmotic water permeability of Necturus gallbladder epithelium[J]. J Gen Physiol, 1989, 93(2): 649-679.
[141] Persson BE, Spring KR. Gallbladder epithelial cell hydraulic water permeability and volume regulation [J]. J Gen Physiol, 1982, 79(6): 481-505.
[142] van Os CH, Slegers JF. Path of osmotic water flow through rabbit gall bladder epithelium[J]. Biochim Biophys Acta, 1973, 291(9): 197-207.
[143] van Os CH, Wiedner G, Wright EM. Volume flows across gallbladder epithelium induced by small hydrostatic and osmotic gradients[J]. J Membr Biol1, 1979, 49(1): 1-20.
[144] Schnermann J, Chou CL, Ma T, et al. Defective proximal tubular fluid reabsorption in transgenic aquaporin-1 null mice[J]. Proc Natl Acad Sci, 1998, 95(5): 9660-9664.
[145] Chou CL, Knepper MA, Hoek AN, et al. Reduced water permeability and altered ultrastructure in thin descending limb of Henle in aquaporin-1 null mice[J]. J Clin Invest, 1999, 103(7): 491-496.
[146] Solenov, E, Watanabe, H, Manley, et al.Sevenfold-reduced osmotic water permeability in primary astrocyte cultures from AQP-4-deficient mice, measured by a fluorescence quenching method[J]. Am J Physiol, 2004, 286(6): C426-432.
[147] Yang B, Zhang H, Verkman AS. Lack of aquaporin-4 water transport inhibition by antiepileptics and arylsulfonamides[J]. Bioorg Med Chem, 2008, 16(1): 7489-7493.
[148] Ruiz-Ederra J, Zhang H, Verkman, AS. Evidence against functional interaction between aquaporin-4 water channels and Kir4.1 K+ channels in retinal Müller cells[J]. J Biol Chem, 2008, 282(23):21866-21872.
[149] Dobbs L, Gonzalez R, Matthay MA, Carter EP, Allen L, Verkman AS. Highly water permeable type I alveolar epithelial cells confer high water permeability between the airspace and vasculature in rat lung[J]. Proc Natl Acad Sci,1998, 95(5): 2991-2996.
[150] Diamond JM. Osmotic water flow in leaky epithelia[J]. J Membr Biol, 1979, 51(5): 195-216.
[151] Spring KR. Routes and mechanism of fluid transport by epithelia [J]. Annu Rev Physiol, 1998, 60(3): 105-119.
[152] Ma T, Jayaraman S, Wang KS, et al. Defective dietary fat processing in transgenic mice lacking aquaporin-1 water channels[J]. Am J Physiol, 2001, 280(2):C126-C134.
[153] Preston GM, Smith BL, Zeidel ML, et al.Mutations in aquaporin-1 in phenotypically normal humans without functional CHIP water channels[J]. Science, 1994, 265(12): 1585-1587.
[154] Bai C, Fukuda N, Song Y, et al.Lung fluid transport in aquaporin-1 and aquaporin-4 knockout mice[J]. J Clin Invest, 1999, 103(9): 555-561.
[155] Ma T, Fukuda N, Song Y, Matthay MA, Verkman AS. Lung fluid transport in aquaporin-5 knockout mice[J]. J Clin Invest, 2000, 105(4): 93-100.
[156] Song Y, Ma T, Matthay MA, Verkman AS. Role of aquaporin-4 in airspace-to-capillary water permeability in intact mouse lung measured by a novel gravimetric method[J]. J Gen Physiol, 2000,115(1):17-27.
[157] Song, Y, Sonawane, N, Verkman, AS. Localization of aquaporin-5 in sweat glands and functional analysis using knockout mice[J]. J Physiol, 2003, 541(9): 561-568.
[158] Yang B, Folkesson HG, Yang J, Matthay MA, Ma T, Verkman AS. Reduced osmotic water permeability of the peritoneal barrier in aquaporin-1 knockout mice [J]. Am J Physiol, 1999, 276(7): C76-81.
[159] Song Y, Yang B, Matthay MA, Ma T, Verkman AS. Role of aquaporin water channels in pleural fluid dynamics[J]. Am J Physiol, 2000, 279(18): C1744-1750.
[160] Verkman, AS, Thiagarajah, JR. Physiology of water transport in the gastrointestinal tract In:Physiology of the Gastrointestinal Tract[M]. LR Johnson, K Barrett, F Ghishan, J Manchant, H Said, J Wood, eds. Vol. 4, New York, Academic Press, p. 2006. 1827-1845.
[161] Moore M, Ma T,Yang B, Verkman, AS. Tear secretion by lacrimal glands in transgenic mice lacking water channels AQP1, AQP3, AQP4 and AQP5[J]. Exp Eye Res, 2000, 70(4): 557-562.
[162] Krane CM, Melvin JE, Nguyen HV, et al. Salivary acinar cells from aquaporin 5-deficient mice have decreased membrane water permeability and altered cell volume regulation [J]. J Biol Chem 2001, 27(12): 23413-23420.
[163] Ma T, Song Y, Gillespie A, Carlson EJ, et al. Defective secretion of saliva in transgenic mice lacking aquaporin-5 water channels[J]. J Biol Chem 1999, 274(23): 20071-20074.
[164] Song, Y, Verkman, AS. Aquaporin-5 dependent fluid secretion in airway submucosal glands[J]. J Biol Chem 2001, 276(19): 41288-41292.
[165] Ma T, Yang B, Gillespie A, et al. Severely impaired urinary concentrating ability in transgenic mice lacking aquaporin-1 water channels[J]. J Biol Chem, 1998, 273(10): 4296-4299.
[166] Oshio K, Watanabe H, Song Y, et al.Reduced cerebrospinal fluid production and intracranial pressure in mice lacking choroid plexus water channel aquaporin-1[J]. J Faseb, 2005, 19(3): 76-78.
[167] Ren G, Cheng A , Melnyk P , et al. Polymorphism in the packing of aquaporin-1 tetramers in 2-D crystals[J]. J Struct Biol, 2000, 130(1): 45-53.
