Short-term metabolic fate of [13N]ammonia in rat liver in vivo

A. J L Cooper, Edward Nieves, A. E. Coleman, S. Filc-DeRicco, A. S. Gelbard

Research output: Contribution to journalArticle

94 Citations (Scopus)

Abstract

The short-term metabolic fate of [13N]ammonia in the livers of adult male, anesthetized rats was determined. Following a bolus injection of tracer quantities of [13N]ammonia into the portal vein, the single pass extraction was ~ 93%, in good agreement with the portal-hepatic vein difference of ~ 90%. High performance liquid chromatographic analysis of deproteinized liver samples indicated that labeled nitrogen is exchanged rapidly among components of: (a) mitochondrial-aspartate aminotransferase and glutamate dehydrogenase reactions and (b) cytoplasmic aspartate aminotransferase and alanine aminotransferase reactions (T( 1/2 ) for the exchange of label toward equilibrium is on the order of seconds). Comparison of specific activities of glutamate and ammonia suggests that a 5 s most labeled glutamate was mitochondrial, whereas at 60 s ~ 93% was cytosolic; this change is presumably brought about by the combined action of the mitochondrial and cytosolic aspartate aminotransferases and the aspartate carrier of the malate-aspartate shuttle. Specific activity measurements of glutamate, alanine, and aspartate are in accord with the proposal by Williamson et al. that the components of the aspartate aminotransferase reaction are in thermodynamic equilibrium, whereas the components of the alanine aminotransferase reaction are in equilibrium but compartmented in the rat liver. Despite considerable label in citrulline at early time points, no radioactivity (≤ 0.25% of the total) was detected in carbamyl phosphate, suggesting very efficient conversion to citrulline with little free carbamyl phosphate accumulating in the mitochondria. Our data also show that some portal vein-derived ammonia is metabolized to glutamine in the rat liver, but the amount is small (~ 7% of that metabolized to urea) in part because liver glutamine synthetase is located in a small population of perivenous cells 'downstream' from the urea cycle-containing periportal cells. Finally, no tracer evidence could be found for the participation of the purine nucleotide cycle in ammonia production from aspartate. The present work continues to emphasize the usefulness of [13N]ammonia for short-term metabolic studies under truly tracer conditions, particularly when turnover times are on the order of seconds.

Original languageEnglish (US)
Pages (from-to)1073-1080
Number of pages8
JournalJournal of Biological Chemistry
Volume262
Issue number3
StatePublished - 1987
Externally publishedYes

Fingerprint

Ammonia
Liver
Rats
Aspartic Acid
Mitochondrial Aspartate Aminotransferase
Portal Vein
Carbamyl Phosphate
Glutamic Acid
Citrulline
Aspartate Aminotransferases
Alanine Transaminase
Cytoplasmic Aspartate Aminotransferase
Urea
Labels
Purine Nucleotides
Glutamate Dehydrogenase
Glutamate-Ammonia Ligase
Mitochondria
Hepatic Veins
Radioactivity

ASJC Scopus subject areas

  • Biochemistry

Cite this

Cooper, A. J. L., Nieves, E., Coleman, A. E., Filc-DeRicco, S., & Gelbard, A. S. (1987). Short-term metabolic fate of [13N]ammonia in rat liver in vivo. Journal of Biological Chemistry, 262(3), 1073-1080.

Short-term metabolic fate of [13N]ammonia in rat liver in vivo. / Cooper, A. J L; Nieves, Edward; Coleman, A. E.; Filc-DeRicco, S.; Gelbard, A. S.

In: Journal of Biological Chemistry, Vol. 262, No. 3, 1987, p. 1073-1080.

Research output: Contribution to journalArticle

Cooper, AJL, Nieves, E, Coleman, AE, Filc-DeRicco, S & Gelbard, AS 1987, 'Short-term metabolic fate of [13N]ammonia in rat liver in vivo', Journal of Biological Chemistry, vol. 262, no. 3, pp. 1073-1080.
Cooper AJL, Nieves E, Coleman AE, Filc-DeRicco S, Gelbard AS. Short-term metabolic fate of [13N]ammonia in rat liver in vivo. Journal of Biological Chemistry. 1987;262(3):1073-1080.
Cooper, A. J L ; Nieves, Edward ; Coleman, A. E. ; Filc-DeRicco, S. ; Gelbard, A. S. / Short-term metabolic fate of [13N]ammonia in rat liver in vivo. In: Journal of Biological Chemistry. 1987 ; Vol. 262, No. 3. pp. 1073-1080.
@article{3d90cfd3321745b9b34991e1f32e2838,
title = "Short-term metabolic fate of [13N]ammonia in rat liver in vivo",
abstract = "The short-term metabolic fate of [13N]ammonia in the livers of adult male, anesthetized rats was determined. Following a bolus injection of tracer quantities of [13N]ammonia into the portal vein, the single pass extraction was ~ 93{\%}, in good agreement with the portal-hepatic vein difference of ~ 90{\%}. High performance liquid chromatographic analysis of deproteinized liver samples indicated that labeled nitrogen is exchanged rapidly among components of: (a) mitochondrial-aspartate aminotransferase and glutamate dehydrogenase reactions and (b) cytoplasmic aspartate aminotransferase and alanine aminotransferase reactions (T( 1/2 ) for the exchange of label toward equilibrium is on the order of seconds). Comparison of specific activities of glutamate and ammonia suggests that a 5 s most labeled glutamate was mitochondrial, whereas at 60 s ~ 93{\%} was cytosolic; this change is presumably brought about by the combined action of the mitochondrial and cytosolic aspartate aminotransferases and the aspartate carrier of the malate-aspartate shuttle. Specific activity measurements of glutamate, alanine, and aspartate are in accord with the proposal by Williamson et al. that the components of the aspartate aminotransferase reaction are in thermodynamic equilibrium, whereas the components of the alanine aminotransferase reaction are in equilibrium but compartmented in the rat liver. Despite considerable label in citrulline at early time points, no radioactivity (≤ 0.25{\%} of the total) was detected in carbamyl phosphate, suggesting very efficient conversion to citrulline with little free carbamyl phosphate accumulating in the mitochondria. Our data also show that some portal vein-derived ammonia is metabolized to glutamine in the rat liver, but the amount is small (~ 7{\%} of that metabolized to urea) in part because liver glutamine synthetase is located in a small population of perivenous cells 'downstream' from the urea cycle-containing periportal cells. Finally, no tracer evidence could be found for the participation of the purine nucleotide cycle in ammonia production from aspartate. The present work continues to emphasize the usefulness of [13N]ammonia for short-term metabolic studies under truly tracer conditions, particularly when turnover times are on the order of seconds.",
author = "Cooper, {A. J L} and Edward Nieves and Coleman, {A. E.} and S. Filc-DeRicco and Gelbard, {A. S.}",
year = "1987",
language = "English (US)",
volume = "262",
pages = "1073--1080",
journal = "Journal of Biological Chemistry",
issn = "0021-9258",
publisher = "American Society for Biochemistry and Molecular Biology Inc.",
number = "3",

}

TY - JOUR

T1 - Short-term metabolic fate of [13N]ammonia in rat liver in vivo

AU - Cooper, A. J L

AU - Nieves, Edward

AU - Coleman, A. E.

AU - Filc-DeRicco, S.

AU - Gelbard, A. S.

PY - 1987

Y1 - 1987

N2 - The short-term metabolic fate of [13N]ammonia in the livers of adult male, anesthetized rats was determined. Following a bolus injection of tracer quantities of [13N]ammonia into the portal vein, the single pass extraction was ~ 93%, in good agreement with the portal-hepatic vein difference of ~ 90%. High performance liquid chromatographic analysis of deproteinized liver samples indicated that labeled nitrogen is exchanged rapidly among components of: (a) mitochondrial-aspartate aminotransferase and glutamate dehydrogenase reactions and (b) cytoplasmic aspartate aminotransferase and alanine aminotransferase reactions (T( 1/2 ) for the exchange of label toward equilibrium is on the order of seconds). Comparison of specific activities of glutamate and ammonia suggests that a 5 s most labeled glutamate was mitochondrial, whereas at 60 s ~ 93% was cytosolic; this change is presumably brought about by the combined action of the mitochondrial and cytosolic aspartate aminotransferases and the aspartate carrier of the malate-aspartate shuttle. Specific activity measurements of glutamate, alanine, and aspartate are in accord with the proposal by Williamson et al. that the components of the aspartate aminotransferase reaction are in thermodynamic equilibrium, whereas the components of the alanine aminotransferase reaction are in equilibrium but compartmented in the rat liver. Despite considerable label in citrulline at early time points, no radioactivity (≤ 0.25% of the total) was detected in carbamyl phosphate, suggesting very efficient conversion to citrulline with little free carbamyl phosphate accumulating in the mitochondria. Our data also show that some portal vein-derived ammonia is metabolized to glutamine in the rat liver, but the amount is small (~ 7% of that metabolized to urea) in part because liver glutamine synthetase is located in a small population of perivenous cells 'downstream' from the urea cycle-containing periportal cells. Finally, no tracer evidence could be found for the participation of the purine nucleotide cycle in ammonia production from aspartate. The present work continues to emphasize the usefulness of [13N]ammonia for short-term metabolic studies under truly tracer conditions, particularly when turnover times are on the order of seconds.

AB - The short-term metabolic fate of [13N]ammonia in the livers of adult male, anesthetized rats was determined. Following a bolus injection of tracer quantities of [13N]ammonia into the portal vein, the single pass extraction was ~ 93%, in good agreement with the portal-hepatic vein difference of ~ 90%. High performance liquid chromatographic analysis of deproteinized liver samples indicated that labeled nitrogen is exchanged rapidly among components of: (a) mitochondrial-aspartate aminotransferase and glutamate dehydrogenase reactions and (b) cytoplasmic aspartate aminotransferase and alanine aminotransferase reactions (T( 1/2 ) for the exchange of label toward equilibrium is on the order of seconds). Comparison of specific activities of glutamate and ammonia suggests that a 5 s most labeled glutamate was mitochondrial, whereas at 60 s ~ 93% was cytosolic; this change is presumably brought about by the combined action of the mitochondrial and cytosolic aspartate aminotransferases and the aspartate carrier of the malate-aspartate shuttle. Specific activity measurements of glutamate, alanine, and aspartate are in accord with the proposal by Williamson et al. that the components of the aspartate aminotransferase reaction are in thermodynamic equilibrium, whereas the components of the alanine aminotransferase reaction are in equilibrium but compartmented in the rat liver. Despite considerable label in citrulline at early time points, no radioactivity (≤ 0.25% of the total) was detected in carbamyl phosphate, suggesting very efficient conversion to citrulline with little free carbamyl phosphate accumulating in the mitochondria. Our data also show that some portal vein-derived ammonia is metabolized to glutamine in the rat liver, but the amount is small (~ 7% of that metabolized to urea) in part because liver glutamine synthetase is located in a small population of perivenous cells 'downstream' from the urea cycle-containing periportal cells. Finally, no tracer evidence could be found for the participation of the purine nucleotide cycle in ammonia production from aspartate. The present work continues to emphasize the usefulness of [13N]ammonia for short-term metabolic studies under truly tracer conditions, particularly when turnover times are on the order of seconds.

UR - http://www.scopus.com/inward/record.url?scp=0023126558&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0023126558&partnerID=8YFLogxK

M3 - Article

C2 - 2879838

AN - SCOPUS:0023126558

VL - 262

SP - 1073

EP - 1080

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

SN - 0021-9258

IS - 3

ER -