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Bile canaliculi contract autonomously by releasing calcium into hepatocytes via mechanosensitive calcium channel. Biomaterials 2020; 259:120283. [PMID: 32827796 DOI: 10.1016/j.biomaterials.2020.120283] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 06/17/2020] [Accepted: 08/01/2020] [Indexed: 12/12/2022]
Abstract
Drug-induced hepatocellular cholestasis leads to altered bile flow. Bile is propelled along the bile canaliculi (BC) by actomyosin contractility, triggered by increased intracellular calcium (Ca2+). However, the source of increased intracellular Ca2+ and its relationship to transporter activity remains elusive. We identify the source of the intracellular Ca2+ involved in triggering BC contractions, and we elucidate how biliary pressure regulates Ca2+ homeostasis and associated BC contractions. Primary rat hepatocytes were cultured in collagen sandwich. Intra-canalicular Ca2+ was measured with fluo-8; and intra-cellular Ca2+ was measured with GCaMP. Pharmacological modulators of canonical Ca2+-channels were used to study the Ca2+-mediated regulation of BC contraction. BC contraction correlates with cyclic transfer of Ca2+ from BC to adjacent hepatocytes, and not with endoplasmic reticulum Ca2+. A mechanosensitive Ca2+ channel (MCC), Piezo-1, is preferentially localized at BC membranes. The Piezo-1 inhibitor GsMTx-4 blocks the Ca2+ transfer, resulting in cholestatic generation of BC-derived vesicles whereas Piezo-1 hyper-activation by Yoda1 increases the frequency of Ca2+ transfer and BC contraction cycles. Yoda1 can recover normal BC contractility in drug-induced hepatocellular cholestasis, supporting that Piezo-1 regulates BC contraction cycles. Finally, we show that hyper-activating Piezo-1 can be exploited to normalize bile flow in drug-induced hepatocellular cholestasis.
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2
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Abstract
We model the dynamics of formation of intercellular secretory lumens. Using conservation laws, we quantitatively study the balance between paracellular leaks and the build-up of osmotic pressure in the lumen. Our model predicts a critical pumping threshold to expand stable lumens. Consistently with experimental observations in bile canaliculi, the model also describes a transition between a monotonous and oscillatory regime during luminogenesis as a function of ion and water transport parameters. We finally discuss the possible importance of regulation of paracellular leaks in intercellular tubulogenesis.
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3
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Jansen PLM. Hydrodynamics of bile flow: Lessons from computational modeling. Hepatology 2018; 67:1624-1627. [PMID: 29077215 DOI: 10.1002/hep.29618] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Accepted: 10/18/2017] [Indexed: 12/07/2022]
Affiliation(s)
- Peter L M Jansen
- Maastricht Centre for Systems Biology (MaCSBio), University of Maastricht, Maastricht, The Netherlands
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4
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Meyer K, Ostrenko O, Bourantas G, Morales-Navarrete H, Porat-Shliom N, Segovia-Miranda F, Nonaka H, Ghaemi A, Verbavatz JM, Brusch L, Sbalzarini I, Kalaidzidis Y, Weigert R, Zerial M. A Predictive 3D Multi-Scale Model of Biliary Fluid Dynamics in the Liver Lobule. Cell Syst 2017; 4:277-290.e9. [PMID: 28330614 DOI: 10.1016/j.cels.2017.02.008] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 11/22/2016] [Accepted: 02/08/2017] [Indexed: 01/15/2023]
Abstract
Bile, the central metabolic product of the liver, is transported by the bile canaliculi network. The impairment of bile flow in cholestatic liver diseases has urged a demand for insights into its regulation. Here, we developed a predictive 3D multi-scale model that simulates fluid dynamic properties successively from the subcellular to the tissue level. The model integrates the structure of the bile canalicular network in the mouse liver lobule, as determined by high-resolution confocal and serial block-face scanning electron microscopy, with measurements of bile transport by intravital microscopy. The combined experiment-theory approach revealed spatial heterogeneities of biliary geometry and hepatocyte transport activity. Based on this, our model predicts gradients of bile velocity and pressure in the liver lobule. Validation of the model predictions by pharmacological inhibition of Rho kinase demonstrated a requirement of canaliculi contractility for bile flow in vivo. Our model can be applied to functionally characterize liver diseases and quantitatively estimate biliary transport upon drug-induced liver injury.
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Affiliation(s)
- Kirstin Meyer
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Saxony 01307, Germany
| | - Oleksandr Ostrenko
- Center for Information Services and High Performance Computing, Technische Universität Dresden, Dresden, Saxony 01062, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, Saxony 01062, Germany
| | - Georgios Bourantas
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Saxony 01307, Germany; Faculty of Science, Technology and Communication, University of Luxembourg, 1359 Luxembourg, Luxembourg; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, Saxony 01062, Germany
| | | | - Natalie Porat-Shliom
- Intracellular Membrane Trafficking Unit, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA
| | - Fabian Segovia-Miranda
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Saxony 01307, Germany
| | - Hidenori Nonaka
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Saxony 01307, Germany
| | - Ali Ghaemi
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Saxony 01307, Germany
| | - Jean-Marc Verbavatz
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Saxony 01307, Germany
| | - Lutz Brusch
- Center for Information Services and High Performance Computing, Technische Universität Dresden, Dresden, Saxony 01062, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, Saxony 01062, Germany
| | - Ivo Sbalzarini
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Saxony 01307, Germany; Faculty of Computer Science, Technische Universität Dresden, Dresden, Saxony 01187, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, Saxony 01062, Germany
| | - Yannis Kalaidzidis
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Saxony 01307, Germany; Faculty of Bioengineering and Bioinformatics, Moscow State University, 119991 Moscow, Russia
| | - Roberto Weigert
- Intracellular Membrane Trafficking Unit, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA
| | - Marino Zerial
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Saxony 01307, Germany; Center for Advancing Electronics Dresden, Technische Universität Dresden, Dresden, Saxony 01062, Germany.
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5
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Sudo R, Kohara H, Mitaka T, Ikeda M, Tanishita K. Coordinated Movement of Bile Canalicular Networks Reconstructed by Rat Small Hepatocytes. Ann Biomed Eng 2005; 33:696-708. [PMID: 15981869 DOI: 10.1007/s10439-005-1690-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Hepatocytes in vivo have a potential for liver regeneration, but it has been very difficult to reconstruct hepatic organoids in vitro. Recent studies have shown that small hepatocytes (SHs) can reconstruct hepatic organoids including functional bile canaliculi (BC). In the present study we analyzed the movement of BC formed in the hepatic organoids, focusing on the coordination of contraction and dilation among cells and the mechanism producing the coordination. Hepatic cells, including SHs, were isolated from an adult rat liver and cultured. Time-lapse images of BC movements were taken and analyzed in cells treated with or without cytochalasin B (CB). Time-lapse images revealed that all BC, regardless of region contracted in a coordinated manner. Actin filaments were observed along the BC even after the BC networks treated with CB dilated markedly. Microinjection of dye was also carried out to investigate the flow thorough BC. Secreted fluorescein from the injected cell flowed along BC, and gap junctional protein connexin 32 was expressed along BC networks, suggesting cell-to-cell communication. Thus, groups of hepatocytes in the hepatic organoids act in a coordinated manner through intercellular communication.
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Affiliation(s)
- Ryo Sudo
- Center for Life Science and Technology, School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
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6
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Gregory RB, Hughes R, Barritt GJ. Induction of cholestasis in the perfused rat liver by 2-aminoethyl diphenylborate, an inhibitor of the hepatocyte plasma membrane Ca2+ channels. J Gastroenterol Hepatol 2004; 19:1128-34. [PMID: 15377289 DOI: 10.1111/j.1440-1746.2004.03417.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
BACKGROUND AND AIMS An increase in the cytoplasmic free Ca2+ concentration in hepatocytes as a result of the release of Ca2+ from intracellular stores and Ca2+ inflow from the extracellular space is a necessary part of the mechanism by which bile acids are moved along the bile cannaliculus by contraction of the cannaliculus. 2-Aminoethyl diphenylborate (2-APB) is a recently discovered inhibitor of store-operated plasma membrane Ca2+ channels in hepatocytes. The aim of the present study was to test the ability of 2-APB to inhibit bile flow. METHODS Bile flow was measured in the isolated perfused rat liver using cannulation of the common bile duct. Measurements were carried out in the presence or absence of 2-APB in either the presence of taurocholic acid (to enhance basal bile flow) or in the absence of taurocholic acid and in the presence of the hormones vasopressin and glucagon, which are known to stimulate bile flow. RESULTS In livers perfused in the presence of taurocholic acid, 2-APB reversibly inhibited bile flow with a slow time of onset. The time of onset of inhibition was reduced by prior addition of the endoplasmic reticulum (Ca(2+) + Mg2+)adenosine triphosphatase inhibitor, 2,5-di-t-butylhydroquinone. In livers perfused in the absence of taurocholate, 2-APB had little effect on the basal rate of bile flow, but inhibited the ability of vasopressin and glucagon to stimulate bile flow. CONCLUSIONS It is concluded that an inhibitor of hepatocyte plasma membrane Ca2+ channels can induce cholestasis. The results provide evidence that suggests that, over a period of time, the normal function of hepatocyte store-operated Ca2+ channels is required to maintain bile flow. Future strategies directed at the regulation of bile flow might include pharmacological or other interventions that modulate Ca2+ inflow to hepatocytes.
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Affiliation(s)
- Roland B Gregory
- Department of Medical Biochemistry, School of Medicine, Faculty of Health Sciences, Flinders University, Adelaide, South Australia, Australia
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7
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Sudo R, Ikeda S, Sugimoto S, Harada K, Hirata K, Tanishita K, Mochizuki Y, Mitaka T. Bile canalicular formation in hepatic organoid reconstructed by rat small hepatocytes and nonparenchymal cells. J Cell Physiol 2004; 199:252-61. [PMID: 15040008 DOI: 10.1002/jcp.10407] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The morphogenesis and movement of bile canaliculi (BC) are not well understood. This is because culture of hepatocytes that maintain polarity of cell membranes and possess highly differentiated functions has never been successful. We found that small hepatocytes (SHs), which are known to be hepatic progenitor cells, could proliferate and differentiate into mature hepatocytes and that BC-like structures developed between rising/piled-up cells. We investigated how BC-like structures developed with maturation of SHs and whether the structures were functionally active as BC. Hepatic cells, including SHs, were isolated from an adult rat liver and cultured. Immunocytochemistry and immunoblotting for BC proteins, such as ectoATPase, 5'-nucleotidase, dipeptidylpeptidase IV, and multidrug-resistance associated protein 2, were examined and time-lapse microscopy was used for the observation of BC contractions. Secretion of bilirubin into the reconstructed BC was also observed. The results of immunocytochemistry, immunoblots, and immunoelectron micrographs revealed that BC proteins were localized in the intercellular space that coincided with BC-like structures reconstructed between rising/piled-up cells. Tight junction-associated protein ZO-1 was also expressed along the BC-like structures. Bilirubin added to the medium were secreted into BC-like structure and accumulated without leakage. Time-lapse microscopy showed continuous contractions of reconstructed BC. In conclusion, BC-like structures reconstructed by SHs may be functional with membrane polarity, secretory ability, and motility. These results show that this culture system may suitable for investigating the mechanism of the formation of BC and their functions.
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Affiliation(s)
- Ryo Sudo
- Department of Pathophysiology, Cancer Research Institute, Sapporo Medical University School of Medicine, Sapporo, Japan
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8
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Wurzinger R, Englisch R, Roka S, Langer R, Roden M, Graf J. Intracellular calcium in the isolated rat liver: correlation to glucose release, K(+) balance and bile flow. Cell Calcium 2001; 30:403-12. [PMID: 11728135 DOI: 10.1054/ceca.2001.0248] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This study correlates whole organ measurements of intracellular calcium concentration ([Ca(2+)](i)) with hormone-induced (epinephrine, vasopressin) changes of liver functions (glucose release, K(+) balance and bile flow). [Ca(2+)](i) was measured in the isolated perfused rat liver using the sensor Fura-2 and applying liver surface fluorescence spectroscopy. The technique was improved by (i) minimizing biliary elimination of the sensor by employing a rat strain deficient in canalicular organic anion transport (TR(-) mutation) and (ii) by correcting for changes of interfering intrinsic organ fluorescence that was shown to depend on the oxidation-reduction state (NAD(P)H content) of the organ. Epinephrine (50 nM) elicits an instantaneous peak rise of [Ca(2+)](i) to approx. 400 nM, followed by a sustained elevation that depends on the presence of extracellular Ca(2+). The rise of [Ca(2+)](i) coincides with initiation of glucose release, transient K(+) uptake, and transient stimulation of bile flow. Vasopressin (2 nM) exerts qualitatively similar effects. The transient rise of bile flow is attributed to Ca(2+)-mediated contraction of the pericanalicular actin-myosin web of hepatocytes.
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Affiliation(s)
- R Wurzinger
- Department of Pathophysiology, University of Vienna, Austria
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9
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Bouscarel B, Kroll SD, Fromm H. Signal transduction and hepatocellular bile acid transport: cross talk between bile acids and second messengers. Gastroenterology 1999; 117:433-52. [PMID: 10419927 DOI: 10.1053/gast.1999.0029900433] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Affiliation(s)
- B Bouscarel
- Division of Gastroenterology and Nutrition, Department of Medicine, George Washington University Medical Center, Washington, D.C., USA
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10
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Hoshino M, Tanaka A, Hayakawa T, Ohiwa T, Katagiri K, Miyaji M, Tsukada K, Takeuchi T. Enhancing effects of vasoconstrictors on bile flow and bile acid excretion in the isolated perfused rat liver. Biochem Pharmacol 1996; 52:489-95. [PMID: 8687504 DOI: 10.1016/0006-2952(96)00252-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The effects of vasoconstrictors on bile flow and bile acid excretion were examined in single-pass isolated perfused rat livers. Administration of norepinephrine (NE), 4 nmol/min, plus continuous infusion of taurocholate (TC) (1.0 mumol/min) rapidly increased bile flow in 1 min, and from min 5 until the end of NE administration (late period) bile flow remained above the basal level (111.7 +/- 2.2%), as did bile acid output (114.6 +/- 1.8%). Without TC infusion, administration of NE produced no increase in the late period. Administration of NE plus taurochenodeoxycholate (1.0 mumol/min) increased bile flow and bile acid output in the late period to 121.9 +/- 7.0 and 137.1 +/- 6.8%, respectively. With NE plus taurodehydrocholate, the respective values were only 105.4 +/- 1.6 and 104.1 +/- 4.0%. When horseradish peroxidase (HRP) (25 mg) was infused over 1 min with continuous NE, the late peak (20-25 min) of HRP elimination into bile significantly exceeded that of untreated controls (P < 0.01). These observations suggest that vasoconstrictors enhance biliary excretion of more hydrophobic bile acids, in part by stimulating vesicular transport.
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Affiliation(s)
- M Hoshino
- First Department of Internal Medicine, Nagoya City University Medical School, Japan
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11
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Suzuki S, Watanabe S, Hirose M, Kitamura T, Oide H, Sato N. Effects of wortmannin, a novel myosin light-chain kinase inhibitor, on bile canalicular contraction in vitro and in vivo. Scand J Gastroenterol 1996; 31:391-7. [PMID: 8726309 DOI: 10.3109/00365529609006416] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
BACKGROUND The cytoskeletal system is believed to play an important role in normal bile formation. The effects of wortmannin, a new myosin light-chain kinase inhibitor, on bile canalicular contraction and bile flow have been observed. METHODS The bile canalicular contraction of cultured hepatocyte doublets was investigated, using an image analyzer with a phase contrast microscope, and the intracellular Ca2+ concentration was measured, using microscopic fluorometry. We also investigated bile flow by in vivo intraportal infusion of the drug in rats. RESULTS Treatment with wortmannin inhibited norepinephrine-induced canalicular contraction and caused a decrease in bile flow without changing systematic and portal blood pressure. Morphologic examination of the electron microscopic study showed that most bile canaliculi were dilated, with loss of microvilli, but no other apparent damage was seen in parenchymal hepatocytes. CONCLUSIONS These data suggest that the integrity of the phosphorylation system of myosin is essential for normal bile flow.
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Affiliation(s)
- S Suzuki
- Dept. of Gastroenterology, Juntendo University School of Medicine, Tokyo, Japan
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12
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Yumoto AU, Watanabe S, Hirose M, Kitamura T, Yamaguchi Y, Sato N. Structural and functional features of bile canaliculi in adult rat hepatocyte spheroids. LIVER 1996; 16:61-6. [PMID: 8868080 DOI: 10.1111/j.1600-0676.1996.tb00705.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Spheroids of adult rat hepatocytes are spherical cell aggregates which retain three-dimensional architecture and hepatocyte specific functions. In this study, we investigated the detailed structure and function of bile canaliculi in spheroids. Hepatocytes were prepared from adult rat liver and cultured with epidermal growth factor (50 ng/ml). Hepatocytes formed floating spheroids 4 days after inoculation. The morphology of hepatocyte spheroids was investigated after fluorescent staining for actin using confocal laser scanning microscopy and electron microscopy. To study the function of bile canaliculi, the transcellular transport of fluorescein diacetate was observed. These experiments were performed in a control group and in a group treated with the actin inhibitor cytochalasin B. In a control group, spheroids contained bile canalicular structures which were surrounded by actin filaments. Added fluorescent dye was secreted and pooled in bile canaliculi. Cytochalasin B caused marked distention of bile canaliculi and prominent accumulation of secreted fluorescent dye in dilated bile canaliculi. This phenomenon was based on the impairment of contractile movement of bile canaliculi. These results demonstrate that hepatocyte spheroids maintain functional and morphological peculiarity, and therefore this model may be useful in investigation of the mechanism of bile formation and intrahepatic cholestasis.
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Affiliation(s)
- A U Yumoto
- Department of Gastroenterology, Juntendo University School of Medicine, Tokyo, Japan
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13
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Karjalainen A, Bygrave FL. Nickel: an agent for investigating the relation between hormone-induced Ca2+ influx and bile flow in the perfused rat liver. Cell Calcium 1995; 18:214-22. [PMID: 8529262 DOI: 10.1016/0143-4160(95)90066-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Influx of Ca2+ induced by the synergistic action of glucagon plus vasopressin in the perfused rat liver was progressively inhibited by infusing increasing concentrations of Ni2+ to the perfusion medium. The onset of Ca2+ influx following vasopressin administration was delayed and inhibition occurred of both the initial rate of Ca2+ influx as well as the total amount of Ca2+ taken up by the liver. Inhibition of the Ca2+ influx rate was almost maximal at approximately 500 microM Ni2+; half-maximal inhibition occurred at less than 250 microM. Added Ni2+ also delayed the onset of the early transient bile flow peak. In addition, the duration of the transient peak in bile flow was prolonged by approximately 2 min by all concentrations of Ni2+ between 25-500 microM, the greatest amount of bile being released in the presence of 250 microM Ni2+. Concentrations of Ni2+ at 100 microM and above also inhibit the decrease in bile flow to below baseline levels. The data identify a multiple role for Ca2+ mobilisation in bile flow.
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Affiliation(s)
- A Karjalainen
- Division of Biochemistry and Molecular Biology, Australian National University, Faculty of Science, Canberra, Australia
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14
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Karjalainen A, Bygrave FL. The synergistic action (cross-talk) of glucagon and vasopressin induces early bile flow and plasma-membrane calcium fluxes in the perfused rat liver. Biochem J 1994; 301 ( Pt 1):187-92. [PMID: 8037669 PMCID: PMC1137160 DOI: 10.1042/bj3010187] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A study was made of the initial responses of perfusate Ca2+ fluxes and bile flow to Ca(2+)-mobilizing agonists, following refinements to the methods for analysing these parameters in the perfused rat liver. Net Ca2+ efflux induced by vasopressin commences at 15 s, reaches a maximal rate at 35 s and declines to zero by 55 s, when Ca2+ influx commences. Vasopressin-induced increases in bile flow commence by 20 s, attain a maximal rate by 35 s and begin to decline at 50 s, to reach basal values by 90 s. Concomitant administration of glucagon modifies each of these actions of vasopressin in the following ways: it decreases by 5 s the time of onset of net Ca2+ efflux, and the time and magnitude of such efflux, and the time of onset of bile flow is decreased to 15 s, and the flow reaches maximal rates by 30 s. When the alpha 1-adrenergic agonist phenylephrine is used in place of vasopressin, Ca2+ efflux commences at 17-18 s and is greater in magnitude; little bile flow is induced by this agonist. Glucagon modifies the action of phenylephrine in the following ways: the onset of Ca2+ efflux is brought forward by 2-3 s, it is of lower magnitude and Ca2+ influx begins by 45 s; bile flow commences by 15-20 s, and reaches a maximum at 30 s, where the rate is much greater than in the absence of glucagon; this rate gradually declines to be near basal by 80 s. The onset of agonist-induced oxygen uptake was also brought forward by the co-administration of glucagon. Comparison of agonist-induced plasma-membrane Ca2+ fluxes and bile flow (with or without glucagon administration) suggests that correlations can be made between net Ca2+ fluxes and the transient increases seen in bile flow.
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Affiliation(s)
- A Karjalainen
- Division of Biochemistry and Molecular Biology, Faculty of Science, Australian National University, Canberra
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15
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Affiliation(s)
- R Coleman
- School of Biochemistry, University of Birmingham, UK
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16
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Affiliation(s)
- M H Nathanson
- Department of Medicine, Yale University School of Medicine, New Haven, Connecticut 06510
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17
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Watanabe S, Miyazaki A, Hirose M, Takeuchi M, Ohide H, Kitamura T, Ueno T, Kominami E, Sato N. Myosin in hepatocytes is essential for bile canalicular contraction. LIVER 1991; 11:185-9. [PMID: 1715965 DOI: 10.1111/j.1600-0676.1991.tb00513.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Active dynamic contraction of bile canaliculi has been observed in cultured doublet hepatocytes using time-lapse cinephotomicrography. This contractile movement plays an important role in normal bile formation. The mechanism of bile canalicular contraction has been proved to involve the Ca(2+)-calmodulin system and pericanalicular actin filaments. However, the role of myosin in this system is still unknown. In this study, using the newly synthesized myosin light-chain kinase inhibitor ML-9, we found that the treatment of cultured doublet hepatocytes with ML-9 inhibited canalicular contraction. This inhibitory effect suggests that myosin is involved in this complex cellular function and that the integrity of the actin-myosin system, as well as the Ca(2+)-calmodulin system is essential for normal bile canalicular contraction.
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Affiliation(s)
- S Watanabe
- Department of Gastroenterology, Juntendo University School of Medicine, Tokyo, Japan
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18
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Grasso JA, Bruno M, Yates AA, Wei LT, Epstein PM. Calmodulin dependence of transferrin receptor recycling in rat reticulocytes. Biochem J 1990; 266:261-72. [PMID: 2310376 PMCID: PMC1131123 DOI: 10.1042/bj2660261] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Kinetic analysis of transferrin receptor properties in 6-8 day rat reticulocytes showed the existence of a single class of high-affinity receptors (Kd 3-10 nM), of which 20-25% were located at the cell surface and the remainder within an intracellular pool. Total transferrin receptor cycling time was 3.9 min. These studies examined the effects of various inhibitors on receptor-mediated transferrin iron delivery in order to define critical steps and events necessary to maintain the functional integrity of the pathway. Dansylcadaverine inhibited iron uptake by blocking exocytic release of transferrin and return of receptors to the cell surface, but did not affect transferrin endocytosis; this action served to deplete the surface pool of transferrin receptors, leading to shutdown of iron uptake. Calmidazolium and other putative calmodulin antagonists exerted an identical action on iron uptake and receptor recycling. The inhibitory effects of these agents on receptor recycling were overcome by the timely addition of Ca2+/ionomycin. From correlative analyses of the effects of these and other inhibitors, it was concluded that: (1) dansylcadaverine and calmodulin antagonists inhibit iron uptake by suppression of receptor recycling and exocytic transferrin release, (2) protein kinase C, transglutaminase, protein synthesis and release of transferrin-bound iron are not necessary for the functional integrity of the iron delivery pathway, (3) exocytic transferrin release and concomitant receptor recycling in rat reticulocytes is dependent upon Ca2+/calmodulin, (4) dansylcadaverine, dimethyldansylcadaverine and calmidazolium act on iron uptake by interfering with calmodulin function, and (5) the endocytotic and exocytotic arms of the iron delivery pathway are under separate regulatory control.
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Affiliation(s)
- J A Grasso
- Department of Anatomy, University of Connecticut Health Center, Storrs 06268
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