Channel-mediated water movement across enclosed or perfused mouse intrahepatic bile duct units

2002 ◽  
Vol 283 (1) ◽  
pp. C338-C346 ◽  
Author(s):  
Ai-Yu Gong ◽  
Anatoly I. Masyuk ◽  
Patrick L. Splinter ◽  
Robert C. Huebert ◽  
Pamela S. Tietz ◽  
...  
Keyword(s):  
Bile Duct ◽  
Water Transport ◽  
Water Movement ◽  
Water Channel ◽  
Intrahepatic Bile Duct ◽  
Enzymatic Digestion ◽  
Bile Formation ◽  
Initial Application ◽  
Luminal Area ◽  
Water Secretion

We previously reported the development of reproducible techniques for isolating and perfusing intact intrahepatic bile duct units (IBDUs) from rats. Given the advantages of transgenic and knockout mice for exploring ductal bile formation, we report here the adaptation of those techniques to mice and their initial application to the study of water transport across mouse intrahepatic biliary epithelia. IBDUs were isolated from livers of normal mice by microdissection combined with enzymatic digestion. After culture, isolated IBDUs sealed to form intact, polarized compartments, and a microperfusion system employing those isolated IBDUs developed. A quantitative image analysis technique was used to observe a rapid increase of luminal area when sealed IBDUs were exposed to a series of inward osmotic gradients reflecting net water secretion; the choleretic agonists secretin and forskolin also induced water secretion into IBDUs. The increase of IBDU luminal area induced by inward osmotic gradients and choleretic agonists was reversibly inhibited by HgCl2, a water channel inhibitor. With the use of a quantitative epifluorescence technique in perfused mouse IBDUs, a high osmotic water permeability ( P f = 2.5–5.6 × 10−2 cm/s) was found in response to osmotic gradients, further supporting the presence of water channels. These findings suggest that, as in the rat, water transport across intrahepatic biliary epithelia in mice is water channel mediated.

Knockdown of hepatocyte aquaporin-8 by RNA interference induces defective bile canalicular water transport

2009 ◽  
Vol 296 (1) ◽  
pp. G93-G100 ◽  
Author(s):  
M. Cecilia Larocca ◽  
Leandro R. Soria ◽  
M. Victoria Espelt ◽  
Guillermo L. Lehmann ◽  
Raúl A. Marinelli
Keyword(s):  
Rna Interference ◽  
Water Transport ◽  
Hepg2 Cells ◽  
Water Movement ◽  
Rat Hepatocytes ◽  
Conclusive Evidence ◽  
Osmotic Gradient ◽  
Bile Formation ◽  
Canalicular Membrane ◽  
Water Secretion

Aquaporin-8 (AQP8) water channels, which are expressed in rat hepatocyte bile canalicular membranes, are involved in water transport during bile formation. Nevertheless, there is no conclusive evidence that AQP8 mediates water secretion into the bile canaliculus. In this study, we directly evaluated whether AQP8 gene silencing by RNA interference inhibits canalicular water secretion in the human hepatocyte-derived cell line, HepG2. By RT-PCR and immunoblotting we found that HepG2 cells express AQP8 and by confocal immunofluorescence microscopy that it is localized intracellularly and on the canalicular membrane, as described in rat hepatocytes. We also verified the expression of AQP8 in normal human liver. Forty-eight hours after transfection of HepG2 cells with RNA duplexes targeting two different regions of human AQP8 molecule, the levels of AQP8 protein specifically decreased by 60–70%. We found that AQP8 knockdown cells showed a significant decline in the canalicular volume of ∼70% ( P < 0.01), suggesting an impairment in the basal (nonstimulated) canalicular water movement. We also found that the decreased AQP8 expression inhibited the canalicular water transport in response either to an inward osmotic gradient (−65%, P < 0.05) or to the bile secretory agonist dibutyryl cAMP (−80%, P < 0.05). Our data suggest that AQP8 plays a major role in water transport across canalicular membrane of HepG2 cells and support the notion that defective expression of AQP8 causes bile secretory dysfunction in human hepatocytes.

Somatostatin stimulates ductal bile absorption and inhibits ductal bile secretion in mice via SSTR2 on cholangiocytes

2003 ◽  
Vol 284 (5) ◽  
pp. C1205-C1214 ◽  
Author(s):  
Ai-Yu Gong ◽  
Pamela S. Tietz ◽  
Melissa A. Muff ◽  
Patrick L. Splinter ◽  
Robert C. Huebert ◽  
...  
Keyword(s):  
Bile Duct ◽  
Knockout Mice ◽  
Somatostatin Receptor ◽  
Fluid Secretion ◽  
Intracellular Camp ◽  
Fluid Absorption ◽  
Wild Type ◽  
Bile Formation ◽  
Luminal Area ◽  
Ductal Fluid

With an in vitro model using enclosed intrahepatic bile duct units (IBDUs) isolated from wild-type and somatostatin receptor (SSTR) subtype 2 knockout mice, we tested the effects of somatostatin, secretin, and a selective SSTR2 agonist (L-779976) on fluid movement across the bile duct epithelial cell layer. By RT-PCR, four of five known subtypes of SSTRs (SSTR1, SSTR2A/2B, SSTR3, and SSTR4, but not SSTR5) were detected in cholangiocytes in wild-type mice. In contrast, SSTR2A/2B were completely depleted in the SSTR2 knockout mice whereas SSTR1, SSTR3 and SSTR4 were expressed in these cholangiocytes. Somatostatin induced a decrease of luminal area of IBDUs isolated from wild-type mice, reflecting net fluid absorption; L-779976 also induced a comparable decrease of luminal area. No significant decrease of luminal area by either somatostatin or L-779976 was observed in IBDUs from SSTR2 knockout mice. Secretin, a choleretic hormone, induced a significant increase of luminal area of IBDUs of wild-type mice, reflecting net fluid secretion; somatostatin and L-779976 inhibited ( P< 0.01) secretin-induced fluid secretion. The inhibitory effect of both somatostatin and L-779976 on secretin-induced IBDU secretion was absent in IBDUs of SSTR2 knockout mice. Somatostatin induced an increase of intracellular cGMP and inhibited secretin-stimulated cAMP synthesis in cholangiocytes; depletion of SSTR2 blocked these effects of somatostatin. These data suggest that somatostatin regulates ductal bile formation in mice not only by inhibition of ductal fluid secretion but also by stimulation of ductal fluid absorption via interacting with SSTR2 on cholangiocytes, a process involving the intracellular cAMP/cGMP second messengers.

Intrahepatic bile ducts transport water in response to absorbed glucose

2002 ◽  
Vol 283 (3) ◽  
pp. C785-C791 ◽  
Author(s):  
Anatoly I. Masyuk ◽  
Tatyana V. Masyuk ◽  
Pamela S. Tietz ◽  
Patrick L. Splinter ◽  
Nicholas F. LaRusso
Keyword(s):  
Water Absorption ◽  
Water Transport ◽  
Bile Flow ◽  
Intrahepatic Bile Duct ◽  
In Vivo Studies ◽  
Dependent Manner ◽  
Bile Formation ◽  
Intraportal Infusion

The physiological relevance of the absorption of glucose from bile by cholangiocytes remains unclear. The aim of this study was to test the hypothesis that absorbed glucose drives aquaporin (AQP)-mediated water transport by biliary epithelia and is thus involved in ductal bile formation. Glucose absorption and water transport by biliary epithelia were studied in vitro by microperfusing intrahepatic bile duct units (IBDUs) isolated from rat liver. In a separate set of in vivo experiments, bile flow and absorption of biliary glucose were measured after intraportal infusion of d-glucose or phlorizin. IBDUs absorbedd-glucose in a dose- and phlorizin-dependent manner with an absorption maximum of 92.8 ± 6.2 pmol · min−1 · mm−1. Absorption of d-glucose by microperfused IBDUs resulted in an increase of water absorption ( J v = 3−10 nl · min−1 · mm−1, P f = 40 × 10−3 cm/sec). Glucose-driven water absorption by IBDUs was inhibited by HgCl2, suggesting that water passively follows absorbed d-glucose mainly transcellularly via mercury-sensitive AQPs. In vivo studies showed that as the amount of absorbed biliary glucose increased after intraportal infusion ofd-glucose, bile flow decreased. In contrast, as the absorption of biliary glucose decreased after phlorizin, bile flow increased. Results support the hypothesis that the physiological significance of the absorption of biliary glucose by cholangiocytes is likely related to regulation of ductal bile formation.

scholarly journals CHIP28 water channels are localized in constitutively water-permeable segments of the nephron.

1993 ◽  
Vol 120 (2) ◽  
pp. 371-383 ◽  
Author(s):  
S Nielsen ◽  
B L Smith ◽  
E I Christensen ◽  
M A Knepper ◽  
P Agre
Keyword(s):  
Proximal Tubule ◽  
Water Transport ◽  
Brush Border ◽  
Water Movement ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Light And Electron Microscopy ◽  
Water Channel ◽  
Proximal Tubules ◽  
Basolateral Membranes

The sites of water transport along the nephron are well characterized, but the molecular basis of renal water transport remains poorly understood. CHIP28 is a 28-kD integral protein which was proposed to mediate transmembrane water movement in red cells and kidney (Preston, G. M., T. P. Carroll, W. B. Guggino, and P. Agre. 1992. Science [Wash. DC]. 256:385-387). To determine whether CHIP28 could account for renal epithelial water transport, we used specific polyclonal antibodies to quantitate and localize CHIP28 at cellular and subcellular levels in rat kidney using light and electron microscopy. CHIP28 comprised 3.8% of isolated proximal tubule brush border protein. Except for the first few cells of the S1 segment, CHIP28 was immunolocalized throughout the convoluted and straight proximal tubules where it was observed in the microvilli of the apical brush border and in basolateral membranes. Very little CHIP28 was detected in endocytic vesicles or other intracellular structures in proximal tubules. Uninterrupted, heavy immunostaining of CHIP28 was also observed over both apical and basolateral membranes of descending thin limbs, including both short and long loops of Henle. These nephron sites have constitutively high osmotic water permeabilities. CHIP28 was not detected in ascending thin limbs, thick ascending limbs, or distal tubules, which are highly impermeable to water. Moreover, CHIP28 was not detected in collecting duct epithelia, where water permeability is regulated by antidiuretic hormone. These determinations of abundance and structural organization provide evidence that the CHIP28 water channel is the predominant pathway for constitutive transepithelial water transport in the proximal tubule and descending limb of Henle's loop.

Localized Intrahepatic Bile Duct Dilatation without a Visible Mass or Stone as depicted on CT Images: Findings of Malignancy Prediction

2008 ◽  
Vol 59 (3) ◽  
pp. 163
Author(s):  
Ju Wan Choi ◽  
Gab Chul Kim ◽  
Han Young Jeong ◽  
Hui Joong Lee ◽  
Jae Hyuck Lee ◽  
...  
Keyword(s):  
Bile Duct ◽  
Intrahepatic Bile Duct ◽  
Ct Images ◽  
Bile Duct Dilatation ◽  
Duct Dilatation

A novel technique for mapping biopsy of bile duct cancer

Endoscopy ◽  
2020 ◽  
Author(s):  
Hirokazu Okada ◽  
Norimitsu Uza ◽  
Tomoaki Matsumori ◽  
Shimpei Matsumoto ◽  
Yuya Muramoto ◽  
...  
Keyword(s):  
Bile Duct ◽  
Intrahepatic Bile Duct ◽  
Preoperative Assessment ◽  
Median Number ◽  
Novel Technique ◽  
Minimal Trauma ◽  
Adequate Sampling ◽  
Novel Method ◽  
Longitudinal Extension ◽  
Mapping Biopsy

Abstract Background Accurate preoperative assessment of the longitudinal extension of perihilar cholangiocarcinoma (PHCC) is essential for treatment planning. Mapping biopsies for PHCC remain challenging owing to technical difficulties and insufficient sample amounts. The aim of this study was to investigate the usefulness of a novel technique for mapping biopsies of PHCC. Methods Our novel method focused on a biliary stent delivery system for mapping biopsies. Fifty patients with PHCC undergoing endoscopic transpapillary mapping biopsy using the novel method were reviewed from August 2015 to June 2019. Results The median number of biopsy samples was six (range 1 – 17), and the rate of adequate sampling was 91.4 % (266 /291). Biopsy from the intrahepatic bile duct was possible in 82.0 % of patients (41 /50), and negative margins were confirmed in the resected specimens from 34 /39 patients who underwent surgery (87.2 %). None of the patients had post-endoscopic retrograde cholangiopancreatography pancreatitis. Conclusions With our novel method, accurate assessment of the longitudinal extension of PHCC might be expected with minimal trauma to the duodenal papilla.

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