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Pflügers Archiv

, Volume 428, Issue 5–6, pp 552–560 | Cite as

Effects of urea on K+ fluxes and cell volume in perfused rat liver

  • Christian Hallbrucker
  • Stephan vom Dahl
  • Markus Ritter
  • Florian Lang
  • Dieter Häussinger
Heart, Circulation, Respiration and Blood; Environmental and Exercise Physiology

Abstract

Exposure of the perfused rat liver to a perfusate made hyperosmotic by the presence of 200 mmol l−1glucose led, as expected, to marked, transient hepatocellular shrinkage followed by volume-regulatory net K+ uptake. However, even after this volume-regulatory K+ uptake had ceased, the liver cells are still slightly shrunken. Withdrawal of glucose from the perfusate resulted in marked transient cell swelling, net K+ release from the liver and restoration of cell volume. However, when the Krebs-Henseleit perfusate was made hyperosmotic by the presence of urea (20–300 mM), there was no immediate decrease in liver mass, yet a slight and persistent cell shrinkage developing 2 min after the onset of exposure to urea. Surprisingly, urea induced concentration-dependent net K+ efflux from the liver and removal of urea net K+ reuptake from the inflowing perfusate. The urea (200 mM)-induced net K+ release resembled that observed following a lowering of the influent [NaCl]: making the perfusate hypoosmotic (245 mosmol l−1, by reducing influent [NaCl] by 30 mM) gave roughly the same K+ response as hyperosmotic exposure (505 mosmol/l) resulting from the presence of 200 mM urea. The urea-induced K+ efflux was not inhibited in the presence of ouabain (1 mM), or in Ca++-free perfusion, but was modified in the presence of quinidine (1 mM) or Ba++ (1 mM). The direction in which the liver was perfused had no effect on the urea-induced net K+ release. Electrophysiological studies showed that urea led to quinidine-sensitive hyperpolarization and increase in K+ selectivity of plasma membranes, suggesting opening of K+ channels in the hepatocyte plasma membrane in response to urea. The data suggest that urea, but not glucose, enters the hepatocyte as quickly as water. Furthermore, urea at high concentrations apparently leads to K+ efflux from the hepatocyte and cell shrinkage, possibly due to opening of K+ channels in the hepatocyte plasma membrane.

Key words

Perfused liver Cell volume regulation Urea K+ fluxes Membrane potential K+ channels Glucose 

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References

  1. 1.
    Chamberlin ME, Strange K (1989) Anisosmotic cell volume regulation: a comparative view. Am J Physiol 257: C159-C173Google Scholar
  2. 2.
    Corasanti JG, Gleeson D, Boyer J (1990) Effects of osmotic stresses on isolated rat hepatocytes. I. Ionic mechanisms of cell volume regulation. Am J Physiol 258: G290-G298Google Scholar
  3. 3.
    Dahl S vom, Hallbrucker C, Lang F, Gerok W, Häussinger D (1991) A non-invasive technique for cell volume determination in perfused rat liver. Biol Chem Hoppe-Seyler 372: 411–418Google Scholar
  4. 4.
    Dahl S vom, Hallbrucker C, Lang F, Häussinger D (1991) Regulation of liver cell volume in the perfused rat liver by hormones. Biochem J 280: 105–109Google Scholar
  5. 5.
    Fukumoto H, Seino S, Imura H, Seino Y, Eddy RL et al (1988) Sequence, tissue distribution and chromosomal localization of mRNA encoding in human glucose transporter-like protein. Proc Natl Acad Sci USA 85: 5434–5438Google Scholar
  6. 6.
    Gould GW, Thomas HM, Jess TJ, Bell GI (1991) Expression of human glucose transporters in Xenopus oocytes: kinetic characterization and substrate specificities of the erythrocyte (GLUT1), liver (GLUT2) and brain (GLUT3) isoforms. Biochemistry 30: 5139–5145Google Scholar
  7. 7.
    Graf J, Haddad P, Häussinger D, Lang, F (1988) Cell volume regulation in liver. Renal Physiol Biochem 3–5: 202–220Google Scholar
  8. 8.
    Grisolia S, Baguena R, Mayor F (eds) (1976) The Urea cycle. J Wiley, New YorkGoogle Scholar
  9. 9.
    Haddad P, Graf J (1989) Volume-regulatory K+ fluxes in the isolated perfused rat liver: characterization by ion transport inhibitors. Am J Physiol 257: G357-G363Google Scholar
  10. 10.
    Haddad P, Thalhammer T, Graf J (1989) Effect of hypertonic stress on liver cell volume, bile flow and volume-regulatory K+ fluxes. Am J Physiol 256: G563-G569Google Scholar
  11. 11.
    Hallbrucker C, vom Dahl S, Lang F, Häussinger D (1991) Control of hepatic proteolysis by amino acids: the role of cell volume. Eur J Biochem 197: 717–724Google Scholar
  12. 12.
    Hallbrucker C, Ritter M, Lang F, Gerok W, Häussinger D (1993) Hydroperoxide metabolism in rat liver. K+ channel activation, cell volume changes and eicosanoid formation. Eur J Biochem 211: 449–458Google Scholar
  13. 13.
    Häussinger D (1983) Hepatocyte heterogeneity in glutamine and ammonia metabolism and the role of an intercellular glutamine cycle during ureogenesis in perfused rat liver. Eur J Biochem 133: 269–275Google Scholar
  14. 14.
    Häussinger D, Lang F (1991) Cell volume in the regulation of hepatic function: a mechanism for metabolic control. Biochim Biophys Acta 1071: 331–350Google Scholar
  15. 15.
    Häussinger D, Stehle T, Lang F (1990) Volume regulation in liver: further characterization by inhibitors and ionic substitutions. Hepatology 11: 243–254Google Scholar
  16. 16.
    Hansen CA, Mah S, Williamson JR (1986) Formation and metabolism of 1,3,4,5-inositol-tetrakisphosphate in liver. J Biol Chem 261: 8100–8103Google Scholar
  17. 17.
    Kellis JT, Nyberg K, Sali D, Fersht AR (1988) Contribution of hydrophobic interactions to protein structure. Nature 333: 784–786Google Scholar
  18. 18.
    Knepper MA, Roch-Ramel F (1987) Pathways of urea transport in the mammalian kidney. Kidney Int 31: 629–633Google Scholar
  19. 19.
    Knepper MA, Star RA (1990) Vasopressin-regulated urea transporter in renal inner medullary collecting duct. Am J Physiol 259: F393-F401Google Scholar
  20. 20.
    Krebs HA, Henseleit K (1932) Untersuchungen über die Harnstoffbildung im Tierkörper. Z Physiol Chem 210: 33–66Google Scholar
  21. 21.
    Lang F, Oberleithner H, Giebisch G (1986) Electrophysiological heterogeneity of proximal convoluted tubules in Amphiuma kidney. Am J Physiol 251: F1063-F1072Google Scholar
  22. 22.
    Lang F, Stehle T, Häussinger D (1989) Water, K+, H+, lactate and glucose fluxes during cell volume regulation in perfused rat liver. Pflügers Arch Physiol 413: 209–216Google Scholar
  23. 23.
    Macey RI (1984) Transport of water and urea in red blood cells. Am J Physiol 246: C195-C203Google Scholar
  24. 24.
    Meijer AJ, Lamers W, Chamaleau RAFM (1990) Nitrogen metabolism and ornithine cycle function. Physiol Rev 70: 701–748Google Scholar
  25. 25.
    Menyhart J, Grof J (1977) Urea as a selective inhibitor of argininosuccinate lyase. Eur J Biochem 77: 405–409Google Scholar
  26. 26.
    Messner G, Wang W, Paulmichl M, Oberleithner H, Lang F (1985) Ouabain decreases apparent potassium-conductance in proximal tubules of the amphibian kidney. Pflügers Arch 404: 131–137Google Scholar
  27. 27.
    Pessin JE, Bell GJ (1992) Mammalian facilitative glucose transporter family: structure and molecular regulation. Annu Rev Physiol 54: 911–930Google Scholar
  28. 28.
    Saha N, Schreiber R, Dahl S vom, Lang F, Gerok W, Häussinger D (1993) Endogenous hydroperoxide formation, cell volume and cellular K+ balance in perfused rat liver. Biochem J 296: 701–707Google Scholar
  29. 29.
    Sies H (1978) The use of perfusion of liver and other organs for the study of microsomal electron transport and cytochrome P450 systems. Methods Enzymol 52: 48–59Google Scholar
  30. 30.
    Thorens B, Cheng ZQ, Brown D, Lodish HF (1990) Liver glucose transporter: a basolateral protein in hepatocytes and intestine and kidney cells. Am J Physiol 259: C279-C285Google Scholar

Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • Christian Hallbrucker
    • 1
  • Stephan vom Dahl
    • 1
  • Markus Ritter
    • 2
  • Florian Lang
    • 3
  • Dieter Häussinger
    • 1
  1. 1.Medizinische Universitätsklinik FreiburgFreiburgGermany
  2. 2.Physiologisches Institut der Universität InnsbruckInnsbruckAustria
  3. 3.Physiologisches Institut der Universität TübingenTübingenGermany

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