Expression and immunolocalization of aquaporin water channels in rat exocrine pancreas

Hurley, Patricia; Ferguson, Carole J.; Kwon, Tae Hwan; Andersen, M L; Norman, Alexander G.; Steward, Martin C.; Nielsen, Søren; Case, R. M.

doi:10.1152/ajpgi.2001.280.4.g701

Cited by 59 publications

(62 citation statements)

References 34 publications

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“…In this case, it is likely that HgCl 2 in addition to altering the concentration gradient was interfering also with regulation of cell volume [23]. We observed extreme cell swelling under the microscope in the present investigation, especially at the higher concentration of 100 mM.…”

Section: Discussionsupporting

confidence: 41%

“…Nerve and muscle membranes are also affected by mercuric chloride (HgCl 2 ) and MeHg [3,6,7,12,25,34,39], and voltage-activated calcium [10,28,29,37,41,46], sodium [38], chloride [12,23] and potassium (K + ) [11,15,18,38] channels are similarly suppressed. The GABA receptor channel [5,22,36], the Na, K-ATPase pump and excitatory amino acid receptors [31] have also been the target of Hg 2 + modulation.…”

Section: Introductionmentioning

confidence: 99%

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Mercury (Hg2+) suppression of potassium currents of outer hair cells

Guihua

Järlebark

Ulfendahl

et al. 2003

Neurotoxicology and Teratology

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The heavy metal mercury (Hg 2 + ) is an insidious environmental pollutant that causes toxic effects on sensory systems. It is well known that the group IIB divalent cation Hg 2 + is an inhibitor of the group I monovalent potassium (K + ) cation pore-forming channel in several biological preparations. Here, we used the whole cell patch clamp technique on freshly isolated outer hair cells (OHCs) of the guinea pig cochlea to record outward K + currents and inward K + currents treated with mercuric chloride (HgCl 2 ). HgCl 2 affected K + currents in a voltage-and dose-dependent manner. The effects of HgCl 2 at 1.0 -100 mM are more pronounced on onset peak current than on steady-state end current. HgCl 2 depolarized also the resting membrane potential. Although the effect of HgCl 2 at 1.0 mM was partially washed out over several minutes, the effects at 10 and 100 mM were irreversible to washout. Since K + channels of OHCs are targets for HgCl 2 ototoxicity, this may lead to auditory transduction problems, including a loss in hearing sensitivity. A better understanding of fundamental mechanisms underlying K + channelopathies in OHCs due to HgCl 2 poisoning may lead to better preventive or therapeutic agents. D

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Section: Discussionsupporting

confidence: 41%

Section: Introductionmentioning

confidence: 99%

Mercury (Hg2+) suppression of potassium currents of outer hair cells

Guihua

Järlebark

Ulfendahl

et al. 2003

Neurotoxicology and Teratology

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“…d-cAMP caused a significant increase in canalicular secretion, and this effect could be completely abrogated by both Me 2 SO and phloretin. *, p Ͻ 0.05. sion has also been demonstrated on the luminal side of seminiferous tubules, the apical membrane of pancreatic acinar cells, and in both absorptive epithelia of the colon and acinar cells of the salivary gland; whether AQP8 in these tissues is also regulated by a trafficking mechanism has not been explored (10,(33)(34)(35)(36).…”

Section: Fig 7 D-camp-induced Bile Secretionmentioning

confidence: 99%

Expression and Localization of Aquaporin Water Channels in Rat Hepatocytes

Huebert¹,

Splinter²,

García³

et al. 2002

Journal of Biological Chemistry

142

190

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Although bile formation requires that large volumes of water be rapidly transported across liver epithelia, including hepatocytes, the molecular mechanisms by which water is secreted into bile are obscure. The aquaporins are a family of 10 channel-forming, integral membrane proteins of ϳ28 kDa numbered 0 -9 that allow water to rapidly traverse epithelial barriers in several organs including kidney, eye, and brain. We found transcripts of three of 10 aquaporins in hepatocytes (aquaporin 8 > > aquaporin 9 > aquaporin 0) by reverse transcription-polymerase chain reaction and quantitative ribonuclease protection assays; immunohistochemistry confirmed the presence of these three proteins in liver. Immunoblots of subcellular fractions of hepatocytes showed enrichment of aquaporins 0 and 8 in microsomes and canalicular plasma membranes; aquaporin 9 was enriched only in basolateral plasma membranes. Immunofluorescence of hepatocyte couplets confirmed the intracellular/canalicular localization of aquaporins 0 and 8 and the basolateral localization of aquaporin 9. Upon exposure of couplets to a choleretic stimulus (i.e. dibutyryl cAMP), aquaporin 8 redistributed to the canalicular plasma membrane; the subcellular distributions of aquaporins 0 and 9 were unaffected. In addition, exposure of couplets to dibutyryl cAMP caused an increase in canalicular water transport in the presence and absence of an osmotic gradient, an effect that was blocked by aquaporin inhibitors. These results provide evidence that aquaporins are present in hepatocytes and that aquaporins are involved in agonist-stimulated canalicular bile secretion.Primary bile is secreted by hepatocytes at the bile canaliculus and is modified via absorption and secretion of water, ions, and solutes by cholangiocytes, the epithelial cells that line the intrahepatic bile ducts. Hepatocytes are polarized epithelial cells that possess well defined canalicular and basolateral plasma membranes and are capable of rapidly transporting large volumes of water (1). Bile consists of 99% water, and water transport by hepatocytes is thought to occur passively in response to local, transient, osmotic gradients generated by the active transport of osmotically active solutes, especially bile acids (2). Two pathways exist by which water could potentially move from blood to bile across the hepatocyte epithelial barrier: a paracellular pathway through the tight junctions between adjacent hepatocytes and a transcellular pathway across hepatocytes. Furthermore, transcellular water movement across individual hepatocytes could theoretically occur either by diffusion through the lipid portion of the sinusoidal and canalicular hepatocyte plasma membranes or through aquaporin water channels, proteins that span the plasma membrane and allow for bi-directional, passive flux of water in response to soluteinduced osmotic gradients. The quantitative contributions of these potential pathways (i.e. paracellular versus transcellular) and mechanisms (i.e. diffusion versus channel-mediated) of water tr...

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“…Here we report the generation of MDCK-II cells stably transfected with AQP5 (RW5 cells) or AQP8 (RW8 cells). Cell culture systems for the study of AQP5 and AQP8 sorting are of physiological import as (i) AQP5 has been shown to play a role in salivary secretion (3,16), (ii) the missorting of AQP5 occurring in patients suffering from Sjogren's syndrome has been suggested to contribute to the disease-related deficiency in fluid secretion (13,14), and (iii) AQP8 has been suggested to play a role in pancreatic (17), liver (18), and gastrointestinal (19) secretion. This is the first report of polarized epithelial cell cultures with AQPs 5 and 8 expressed functionally and in a polarized fashion, and the first evidence of the basolateral sorting of AQP8 in a polarized epithelial cell.…”

mentioning

confidence: 99%