scholarly journals The purine nucleotide cycle and ammonia formation from glutamine by rat kidney slices

1983 ◽  
Vol 212 (3) ◽  
pp. 705-711 ◽  
Author(s):  
T Strzelecki ◽  
J Rogulski ◽  
S Angielski
Keyword(s):  
Adenine Nucleotides ◽  
Rat Kidney ◽  
Glucose Production ◽  
Amino Group ◽  
Purine Nucleotide ◽  
Normal Kidney ◽  
Kidney Slices ◽  
Total Ammonia ◽  
Purine Nucleotide Cycle ◽  
Ammonia Formation

To test the significance of the purine nucleotide cycle in renal ammoniagenesis, studies were conducted with rat kidney cortical slices using glutamate or glutamine labelled in the alpha-amino group with 15N. Glucose production by normal kidney slices with 2 mM-glutamine was equal to that with 3 mM-glutamate. With L-[15N]glutamate as sole substrate, one-third of the total ammonia produced by kidney slices was labelled, indicating significant deamination of glutamate or other amino acids from the cellular pool. Ammonia produced from the amino group of L-[alpha-15N]glutamine was 4-fold higher than from glutamate at similar glucose production rates. Glucose and ammonia formation from glutamine by kidney slices obtained from rats with chronic metabolic acidosis was found to be 70% higher than by normal kidney slices. The contribution of the amino group of glutamine to total ammonia production was similar in both types of kidneys. No 15N was found in the amino group of adenine nucleotides after incubation of kidney slices from normal or chronically acidotic rats with labelled glutamine. Addition of Pi, a strong inhibitor of AMP deaminase, had no effect on ammonia formation from glutamine. Likewise, fructose, which may induce a decrease in endogenous Pi, had no effect on ammonia formation. The data obtained suggest that the contribution of the purine nucleotide cycle to ammonia formation from glutamine in rat renal tissue is insignificant.

scholarly journals Sources of ammonia for mammalian urea synthesis

1978 ◽  
Vol 176 (3) ◽  
pp. 733-737 ◽  
Author(s):  
H A Krebs ◽  
R Hems ◽  
P Lund ◽  
D Halliday ◽  
W W Read
Keyword(s):  
Glutamate Dehydrogenase ◽  
Initial Rate ◽  
Adenine Nucleotides ◽  
Rat Hepatocytes ◽  
The Other ◽  
Amino Group ◽  
Urea Synthesis ◽  
Purine Nucleotide ◽  
Carbamoyl Phosphate ◽  
Purine Nucleotide Cycle

The initial rate of incorporation of [15N]alanine into the 6-amino group of the adenine nucleotides in rat hepatocytes was about one-eighteenth of the rate of incorporation into urea. Thus the purine nucleotide cycle cannot provide most of the ammonia needed in urea synthesis for the carbamoyl phosphate synthase reaction (EC 2.7.2.5). On the other hand, contrary to the view expressed by McGivan & Chappell [(1975) FEBS Lett. 52, 1–7], the experiments support the view that hepatic glutamate dehydrogenase can supply the required ammonia.

Renal gluconeogenesis, adenine nucleotides, and enzyme activities

1968 ◽  
Vol 46 (11) ◽  
pp. 1345-1349 ◽  
Author(s):  
S. J. Patrick
Keyword(s):  
Enzyme Activities ◽  
Adenine Nucleotide ◽  
Adenine Nucleotides ◽  
Rat Kidney ◽  
Glucose Production ◽  
Key Enzymes ◽  
Kidney Slices ◽  
Renal Gluconeogenesis

Various drugs which alter rates of glucose production by rat kidney slices from pyruvate or other substrates were found to have marked effects on the relative contents of ATP, ADP, and AMP in the kidney slices. The effects of the changes in adenine nucleotide concentrations on the activity of key enzymes concerned with glycolysis and gluconeogenesis were investigated. The results generally support the concept that the drugs affect gluconeogenesis secondarily by altering the concentrations of the adenine nucleotides in the tissue.

scholarly journals Utilization of [15N]glutamate by cultured astrocytes

1986 ◽  
Vol 234 (1) ◽  
pp. 185-192 ◽  
Author(s):  
M Yudkoff ◽  
I Nissim ◽  
K Hummeler ◽  
M Medow ◽  
D Pleasure
Keyword(s):  
Reductive Amination ◽  
Adenine Nucleotides ◽  
Ammonia Concentration ◽  
Gas Chromatography Mass Spectrometry ◽  
Purine Nucleotide ◽  
Cultured Astrocytes ◽  
Dehydrogenase Reaction ◽  
Purine Nucleotide Cycle ◽  
Almost All ◽  
Glutaminase Activity

The metabolism of 0.25 mM-[15N]glutamic acid in cultured astrocytes was studied with gas chromatography-mass spectrometry. Almost all 15N was found as [2-15N]glutamine, [2-15N]glutamine, [5-15N]glutamine and [15N]alanine after 210 min of incubation. Some incorporation of 15N into aspartate and the 6-amino position of the adenine nucleotides also was observed, the latter reflecting activity of the purine nucleotide cycle. After the addition of [15N]glutamate the ammonia concentration in the medium declined, but the intracellular ATP concentration was unchanged despite concomitant ATP consumption in the glutamine synthetase reaction. Some potential sources of glutamate nitrogen were identified by incubating the astrocytes for 24 h with [5-15N]glutamine, [2-15N]glutamine or [15N]alanine. Significant labelling of glutamate was noted with addition of glutamine labelled on either the amino or the amide moiety, reflecting both glutaminase activity and reductive amination of 2-oxoglutarate in the glutamate dehydrogenase reaction. Alanine nitrogen also is an important source of glutamate nitrogen in this system.

scholarly journals The purine nucleotide cycle. A pathway for ammonia production in the rat kidney.

1976 ◽  
Vol 58 (2) ◽  
pp. 326-335 ◽  
Author(s):  
R T Bogusky ◽  
L M Lowenstein ◽  
J M Lowenstein
Keyword(s):  
Rat Kidney ◽  
Ammonia Production ◽  
Purine Nucleotide ◽  
Purine Nucleotide Cycle

scholarly journals The purine nucleotide cycle in the regulation of ammoniagenesis during induction and cessation of chronic acidosis in the rat kidney

1981 ◽  
Vol 196 (1) ◽  
pp. 323-326 ◽  
Author(s):  
R T Bogusky ◽  
K A Steele ◽  
L M Lowenstein
Keyword(s):  
Glutamate Dehydrogenase ◽  
Rat Kidney ◽  
Recovery Period ◽  
Purine Nucleotide ◽  
Sprague Dawley ◽  
Metabolic Intermediates ◽  
Control Value ◽  
Sprague Dawley Rats ◽  
Purine Nucleotide Cycle ◽  
Subsequent Withdrawal

The effect of chronic acid feeding and its subsequent withdrawal was determined on the amounts of the metabolic intermediates and enzymic activities of the purine nucleotide cycle. Sprague-Dawley rats were given 1.5% (w/v) NH4Cl in their drinking water for 5 days. The renal excretion of NH3 rose 70-fold and the rats developed acidosis. The amount of renal IMP rose from a control value of 4.5 +/- 2.2 to 20.4 +/- 3.7nmol/g of kidney after 48h of acid feeding (P less than 0.001) and fell to normal within 48h of the recovery. Adenylosuccinate concentrations fell from a control value of 4.5 +/- 0.9nmol/g of kidney to 1.2 +/- 0.3nmol/g (P less than 0.005) by day 5 of acidosis and continued to fall to undetectable values by 48h after recovery. The amount of AMP remained constant through the acid-feeding and the recovery periods. The activity of adenylosuccinate synthetase, the rate-limiting enzyme of the purine nucleotide cycle, paralleled the rise and fall in NH3 excretion. The activities of phosphate-dependent glutaminase and glutamate dehydrogenase were elevated during the acid-feeding and the recovery period. Thus changes in the purine nucleotide cycle correlate with changes in NH3 excretion to a more parallel degree than does the activity of glutaminase or glutamate dehydrogenase.

Ammoniagenesis: D-Glutamyltransferase as a Source of Ammonia in the Rat Kidney

1975 ◽  
Vol 53 (8) ◽  
pp. 930-933 ◽  
Author(s):  
P. Wadoux ◽  
T. C. Welbourne
Keyword(s):  
Glutamate Dehydrogenase ◽  
Rat Kidney ◽  
Ammonia Production ◽  
Normal Kidney ◽  
Isolated Perfused Rat Kidney ◽  
Perfused Rat Kidney ◽  
Total Ammonia ◽  
Normal Rat

The contribution of D-glutamyltransferase (D-GT) (EC 2.3.2.1) to total renal ammonia production was determined by employing DL-methionine-DL-sulfoximine (MSO) as an inhibitor of D-GT. Rat kidney homogenates were assayed for NH3-liberating activity under optimal D-GT or γ-glutamyltranspeptidase (γ-GTP) (EC 2.3.2.2) conditions. MSO inhibits only D-GT activity. The contribution of D-GT to total renal ammonia production was then evaluated in the isolated perfused rat kidney employing identical substrate (5 mML-glutamine) and inhibitor (15 mM MSO) concentrations as employed in the homogenate study. Under these conditions, MSO inhibits 70% of the total ammonia production by the normal kidney; in addition, the ratio of ammonia produced per glutamine taken up rose from 1.0 to 1.8. In kidneys from chronically acidotic rats, MSO reduced total ammonia production only 35% while the NH3/glutamine ratio rose from 1.0 to 1.8. D-GT appears to be the predominant source of NH3 production in the normal rat kidney; γ-GTP does not contribute significantly. The rise in the NH3/glutamine ratio after D-GT inhibition is consistent with glutamine utilization via the activated mitochondrial glutaminase (EC 3.5.1.2) – glutamate dehydrogenase (EC 1.4.1.2) pathway.

Effect of Inhibition of Gluconeogenesis on Ammonia Production in the Perfused Rat Kidney

1976 ◽  
Vol 50 (6) ◽  
pp. 493-498 ◽  
Author(s):  
B. D. Ross
Keyword(s):  
Rat Kidney ◽  
Glucose Production ◽  
Ammonia Production ◽  
Primary Event ◽  
Perfused Rat Kidney ◽  
Lactate Uptake ◽  
Ammonia Formation ◽  
Glutamine Uptake

1. Gluconeogenesis from lactate or from glutamine is inhibited by 90–100% by sodium quinolinate (1 mmol/l) or 3-mercaptopicolinate (150 nmol/l) in the perfused rat kidney. l-Tryptophan is not metabolized and is without effect. 2. Lactate uptake and glucose production are inhibited to the same degree by 3-mercaptopicolinate in the kidneys of well-fed or starved rats. 3. Inhibition of gluconeogenesis from glutamine (1 mmol/l) by 3-mercaptopicolinate is accompanied by 50% inhibition of ammonia production, and 34% inhibition of glutamine uptake, in the kidneys of acidotic rats. Ammonia production from glutamine was not inhibited in kidneys from non-acidotic rats. 4. It is concluded that the increased rate of gluconeogenesis from glutamine which occurs in acidotic rats is an essential and primary event regulating all of the increase in ammonia formation.

Effect of acute metabolic acidosis on ammonia metabolism in kidney

1989 ◽  
Vol 256 (2) ◽  
pp. F321-F328
Author(s):  
R. T. Bogusky ◽  
R. L. Dietrich
Keyword(s):  
Metabolic Acidosis ◽  
Glutamate Dehydrogenase ◽  
Rat Kidney ◽  
Methionine Sulfoximine ◽  
Amide Nitrogen ◽  
Ammonia Metabolism ◽  
Perfused Rat Kidney ◽  
Purine Nucleotide Cycle ◽  
Acute Metabolic Acidosis ◽  
Ammonia Formation

To understand the mechanisms that initiate the increase in ammonia formation during acute acidosis in kidney [amino-15N]- and [amino-15N]glutamine were used as substrates in isolated perfused rat kidney experiments. Perfused kidneys from methionine sulfoximine-treated rats take up glutamine nitrogen at the rate of 1.50 +/- 0.08 mumol.g kidney-1.min-1 while forming ammonia at a rate of 0.65 +/- 0.09 mumol.g.kidney-1.min-1. Mass spectrometer analysis of the perfusate and urine reveals that ammonia is formed from the amide nitrogen of glutamine at the rate of 0.32 +/- 0.06 mumol.g kidney-1.min-1 and ammonia is formed from glutamate derived from glutamine at the rate of 0.21 +/- 0.04 mumol.g kidney-1.min-1. The balance of the ammonia formed is from unidentified endogenous sources. Addition of HCl to the perfusate to lower perfusate pH increases ammonia formation to 1.09 +/- 0.10 mumol.g kidney-1.min-1. The results exclude a role for the purine nucleotide cycle during acute acidosis and confirm that ammonia formation from glutamate derived from glutamine is via glutamate dehydrogenase. Lowering perfusate pH increases the rate of glutamine deamidation significantly by 0.33 +/- 0.06 mumol.g kidney-1.min-1 and increases the rate of ammonia formation via glutamate dehydrogenase insignificantly by only 0.08 +/- 0.04 mumol.g kidney-1.min-1, whereas ammonia formation from endogenous sources remains unchanged. The results demonstrate that regulation of glutamine deamidation is an important controlling step in ammonia formation during acute metabolic acidosis in kidney.

scholarly journals The purine nucleotide cycle and ammoniagenesis in rat kidney tubules.

1986 ◽  
Vol 261 (22) ◽  
pp. 10157-10162
Author(s):  
K Tornheim ◽  
H Pang ◽  
C E Costello
Keyword(s):  
Rat Kidney ◽  
Purine Nucleotide ◽  
Kidney Tubules ◽  
Purine Nucleotide Cycle
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