Hepatocyte heterogeneity in glutamate uptake by isolated perfused rat liver

Eur J Biochem. 1983 Nov 2;136(2):421-5. doi: 10.1111/j.1432-1033.1983.tb07759.x.

Abstract

Glutamate is simultaneously taken up and released by perfused rat liver, as shown by 14CO2 production from [1-14C]glutamate in the presence of a net glutamate release by the liver, turning to a net glutamate uptake at portal glutamate concentrations above 0.3 mM. 14CO2 production from portal [1-14C]glutamate is decreased by about 60% in the presence of ammonium ions. This effect is not observed during inhibition of glutamine synthetase by methionine sulfoximine. 14CO2 production from [1-14C]glutamate is not influenced by glutamine. Also, when glutamate accumulates intracellularly during the metabolism of glutamine (added at high concentrations, 5 mM), 14CO2 production from [1-14C]glutamate is not affected. If labeled glutamate is generated intracellularly from added [U-14C]proline, stimulation of glutamine synthesis by ammonium ions did not affect 14CO2 production from [U-14C]proline. After induction of a perivenous liver cell necrosis by CCL4, i.e. conditions associated with an almost complete loss of perivenous glutamine synthesis but no effect on periportal urea synthesis, 14CO2 production from [1-14C]glutamate is decreased by about 70%. The results are explained by hepatocyte heterogeneity in glutamate metabolism and indicate a predominant uptake of glutamate (that reaches the liver by the vena portae) by the small perivenous population of glutamine-synthesizing hepatocytes, whereas glutamate production from glutamine or proline is predominantly periportal. In view of the size of the glutamine synthetase-containing hepatocyte pool [Gebhardt, R. and Mecke, D. (1983) EMBO J. 2, 567-570], glutamate transport capacity of these hepatocytes would be about 20-fold higher as compared to other hepatocytes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Transport
  • Carbon Dioxide / metabolism
  • Chemical Phenomena
  • Chemistry
  • Glutamates / metabolism*
  • Liver / metabolism*
  • Male
  • Perfusion
  • Quaternary Ammonium Compounds / pharmacology
  • Rats
  • Rats, Inbred Strains

Substances

  • Glutamates
  • Quaternary Ammonium Compounds
  • Carbon Dioxide