scholarly journals Glutamine synthesis from aspartate in guinea-pig renal cortex

1990 ◽  
Vol 268 (2) ◽  
pp. 437-442 ◽  
Author(s):  
G Baverel ◽  
G Martin ◽  
C Michoudet
Keyword(s):  
Glutamine Synthetase ◽  
Guinea Pig ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Tricarboxylic Acid Cycle ◽  
Kidney Cortex ◽  
Carbon And Nitrogen ◽  
Ammonia Release ◽  
Glutamine Synthesis ◽  
Methionine Sulphoximine ◽  
Main Carbon

1. Glutamine was found to be the main carbon and nitrogen product of the metabolism of aspartate in isolated guinea-pig kidney-cortex tubules. Glutamate, ammonia and alanine were only minor products. 2. Carbon-balance calculations and the release of 14CO2 from [U-14C]aspartate indicate that oxidation of the aspartate carbon skeleton occurred. 3. A pathway involving aspartate aminotransferase, glutamate dehydrogenase, glutamine synthetase, phosphoenolpyruvate carboxykinase, pyruvate kinase, pyruvate dehydrogenase and enzymes of the tricarboxylic acid cycle is proposed for the conversion of aspartate into glutamine. 4. Evidence for this pathway was obtained by: (i) inhibiting aspartate removal by amino-oxyacetate, an inhibitor of transaminases, (ii) the use of methionine sulphoximine, an inhibitor of glutamine synthetase, which induced a large increase in ammonia release from aspartate, (iii) the use of quinolinate, an inhibitor of phosphoenolpyruvate carboxykinase, which inhibited glutamine synthesis from aspartate, (iv) the use of alpha-cyano-4-hydroxycinnamate, an inhibitor of the mitochondrial transport of pyruvate, which caused an accumulation of pyruvate from aspartate, and (v) the use of fluoroacetate, an inhibitor of aconitase, which inhibited glutamine synthesis with concomitant accumulation of citrate from aspartate.

scholarly journals The conversion of alanine into glutamine in guinea-pig renal cortex. Essential role of pyruvate carboxylase

1981 ◽  
Vol 200 (1) ◽  
pp. 27-33 ◽  
Author(s):  
M Forissier ◽  
G Baverel
Keyword(s):  
Glutamine Synthetase ◽  
Guinea Pig ◽  
Pyruvate Carboxylase ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Kidney Cortex ◽  
Acid Cycle ◽  
Ammonia Release ◽  
Tricarboxylic Acid Cycle Intermediates

1. The metabolism of L-alanine was studied in isolated guinea-pig kidney-cortex tubules. 2. In contrast with previous conclusions of Krebs [(1935) Biochem. J. 29, 1951-1969], glutamine was found to be the main carbon and nitrogenous product of the metabolism of alanine (at 1 and 5 mM). Glutamate and ammonia were only minor products. 3. At neither concentration of alanine was there accumulation of glucose, glycogen, pyruvate, lactate, aspartate or tricarboxylic acid-cycle intermediates. 4. Carbon-balance calculations and the release of 14CO2 from [U-14C]alanine indicate that oxidation of the alanine carbon skeleton occurred at both substrate concentrations. 5. A pathway involving alanine aminotransferase, glutamate dehydrogenase, glutamine synthetase, pyruvate dehydrogenase, pyruvate carboxylase and enzymes of the tricarboxylic acid cycle is proposed for the conversion of alanine into glutamine. 6. Strong evidence for this pathway was obtained by: (i) suppressing alanine removal by amino-oxyacetate, and inhibitor of transaminases, (ii) measuring the release of 14CO2 from [1-14C]alanine, (iii) the use of L-methionine DL-sulphoximine, an inhibitor of glutamine synthetase, which induced a large increase in ammonia release from alanine, and (iv) the use of fluoroacetate, an inhibitor of aconitase, which inhibited glutamine synthesis with concomitant accumulation of citrate from alanine. 7. In this pathway, the central role of pyruvate carboxylase, which explains the discrepancy between our results and those of Krebs (1935), was also demonstrated.

scholarly journals Fate of glutamate carbon and nitrogen in isolated guinea-pig kidney-cortex tubules. Evidence for involvement of glutamate dehydrogenase in glutamine sythesis from glutamate

1980 ◽  
Vol 188 (3) ◽  
pp. 873-880 ◽  
Author(s):  
G Baverel ◽  
C Genoux ◽  
M Forissier ◽  
M Pellet
Keyword(s):  
Guinea Pig ◽  
Glutamate Dehydrogenase ◽  
Carbon Skeleton ◽  
Kidney Cortex ◽  
Glutamate Metabolism ◽  
Carbon And Nitrogen ◽  
Pig Kidney ◽  
Glutamate Concentration ◽  
Rate Limiting Step

1. The pathways and the fate of glutamate carbon and nitrogen were investigated in isolated guinea-pig kidney-cortex tubules. 2. At low glutamate concentration (1 mM), the glutamate carbon skeleton was either completely oxidized or converted into glutamine. At high glutamate concentration (5 mM), glucose, lactate and alanine were additional products of glutamate metabolism. 3. At neither concentration of glutamate was there accumulation of ammonia. 4. Nitrogen-balance calculations and the release of 14CO2 from L-[1-14C]glutamate (which gives an estimation of the flux of glutamate carbon skeleton through alpha-oxoglutarate dehydrogenase) clearly indicated that, despite the absence of ammonia accumulation, glutamate metabolism was initiated by the action of glutamate dehydrogenase and not by transamination reactions as suggested by Klahr, Schoolwerth & Bourgoignie [(1972) Am. J. Physiol. 222, 813-820] and Preuss [(1972) Am. J. Physiol. 222, 1395-1397]. Additional evidence for this was obtained by the use of (i) amino-oxyacetate, an inhibitor of transaminases, which did not decrease glutamate removal, or (ii) L-methionine DL-sulphoximine, an inhibitor of glutamine synthetase, which caused an accumulation of ammonia from glutamate. 5. Addition of NH4Cl plus glutamate caused an increase in both glutamate removal and glutamine synthesis, demonstrating that the supply of ammonia via glutamate dehydrogenase is the rate-limiting step in glutamine formation from glutamate. NH4Cl also inhibited the flux of glutamate through glutamate dehydrogenase and the formation of glucose, alanine and lactate. 6. The activities of enzymes possibly involved in the glutamate conversion into pyruvate were measured in guinea-pig renal cortex. 7. Renal arteriovenous-difference measurements revealed that in vivo the guinea-pig kidney adds glutamine and alanine to the circulating blood.

scholarly journals The effects of starvation and experimental diabetes on phosphoenol-pyruvate carboxykinase in the guinea pig

1977 ◽  
Vol 164 (2) ◽  
pp. 357-361 ◽  
Author(s):  
K R F Elliott ◽  
C I Pogson
Keyword(s):  
Enzyme Activity ◽  
Guinea Pig ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Blood Glucose Concentration ◽  
Mitochondrial Fraction ◽  
Kidney Cortex ◽  
Total Enzyme Activity ◽  
The Mean ◽  
Mean Blood Glucose ◽  
Total Enzyme

1. Approx. 85% of liver phosphoenolpyruvate carboxykinase is associated with the mitochondrial fraction in the fed guinea pig. Enzyme activity is unchanged in diabetes, but doubles during starvation. In contrast with earlier reports, both cytoplasmic and mitochondrial activities were found to be increased. 2. In kidney cortex, total enzyme activity is increased in both starved and diabetic animals. These changes are associated with increases in the cytoplasmic activity alone. 3. In diabetic animals the mean blood-glucose concentration was 23.1 mM. Other blood metabolites were lower than those in the rat, and the animals did not show significant ketosis. 4. Changes in the rates of gluconeogenesis from lactate and propionate paralleled those in phosphoenolpyruvate carboxykinase activity.

scholarly journals Release and fixation of CO2 by guinea-pig kidney tubules metabolizing aspartate

1992 ◽  
Vol 284 (3) ◽  
pp. 697-703
Author(s):  
G Martin ◽  
C Michoudet ◽  
N Vincent ◽  
G Baverel
Keyword(s):  
Guinea Pig ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Co2 Fixation ◽  
Carbon Oxidation ◽  
Kidney Tubules ◽  
Pig Kidney ◽  
Glutamine Synthesis ◽  
Oxoglutarate Dehydrogenase

1. The metabolism of L-[U-14C]aspartate, L-[1-14C]aspartate and L-[4-14C]aspartate was studied in isolated guinea-pig kidney tubules. 2. Oxidation of C-1 plus that of C-4 of aspartate accounted for 90-92% of the CO2 released from aspartate, whereas oxidation of the inner carbon atoms of aspartate (which occurs beyond the 2-oxoglutarate dehydrogenase step) represented only 8-10% of aspartate carbon oxidation. 3. The formation of [1-14C]glutamine and [1-14C]glutamate from [1-14C]aspartate and [4-14C]aspartate indicated that about one-third of the oxaloacetate synthesized from aspartate underwent randomization at the level of fumarate. 4. With [U-14C]aspartate as substrate, the percentage of the C-1 of glutamate and glutamine found radiolabelled after 60 min of incubation was 92.7% and 47.5% in the absence and the presence of bicarbonate respectively. 5. That CO2 fixation occurred at high rates in the presence of bicarbonate was demonstrated by incubating tubules with aspartate plus [14C]bicarbonate; under this condition, the label fixed was found in C-1 of glutamate, glutamine and aspartate, as well as in C-4 of aspartate, demonstrating not only randomization of aspartate carbon but also aspartate resynthesis secondary to oxaloacetate cycling via phosphoenolpyruvate carboxykinase, pyruvate kinase and pyruvate carboxylase. 6. The importance of CO2 fixation in glutamine synthesis from aspartate is discussed in relation to the possible role of the guinea-pig kidney in systemic acid-base regulation in vivo.

scholarly journals The activities and intracellular distribution of nicotinamide-adenine dinucleotide phosphate-malate dehydrogenase, phosphoenolpyruvate carboxykinase and pyruvate carboxylase in rat, guinea-pig and rabbit tissues

1975 ◽  
Vol 146 (2) ◽  
pp. 329-332 ◽  
Author(s):  
D E Saggerson ◽  
C J Evans
Keyword(s):  
Adipose Tissue ◽  
Guinea Pig ◽  
Malate Dehydrogenase ◽  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Intracellular Distribution ◽  
Kidney Cortex ◽  
Carboxylase Activity ◽  
Liver And Kidney

1. Measurements are presented of the activity and intracellular distribution of phosphoenolypruvate carboxykinase, pyruvate carboxylase and NADP-malate dehydrogenase in rat, guinea-pig and rabbit liver and kidney cortex, together with previously obtained measurements of these enzymes in adipose tissue. 2. In all three tissues pyruvate carboxylase activity was greatest in the rat and lowest in the rabbit. 3. Guinea pig and rabbit were very similar to each other with respect to the extramitochondrial-mitochondrial distribution of phosphoenolpyruvate carboxykinase in all three tissues. 4. NADP-malate dehydrogenase was present in all three tissues in the rat, present in kidney cortex and adipose tissue in the guinea pig and absent from all tissues examines in the rabbit.

scholarly journals Glutamine synthesis from glucose and ammonium chloride by guinea-pig kidney tubules

1994 ◽  
Vol 297 (1) ◽  
pp. 69-74 ◽  
Author(s):  
C Michoudet ◽  
M F Chauvin ◽  
G Baverel
Keyword(s):  
Glucose Metabolism ◽  
Guinea Pig ◽  
Carbon Skeleton ◽  
Kidney Cortex ◽  
Physiological Concentration ◽  
Pig Kidney ◽  
Glucose Carbon ◽  
Glutamine Synthesis ◽  
Stimulation Of

1. At a physiological concentration (5 mM), glucose was found to be metabolized by isolated kidney cortex tubules prepared from fed guinea pigs. 2. The release of 14CO2 from [U-14C]glucose indicated that oxidation of the glucose carbon skeleton represented about 50% of the glucose removed; significant amounts of lactate and glutamine also accumulated. 3. Addition of 0.1-10 mM NH4Cl led to a dose-dependent stimulation of glucose metabolism which was accompanied by a large increase in lactate and glutamine accumulation and, to a lesser extent, in glucose oxidation. 4. Comparison of the release of 14CO2 from [1-14C]- and [6-14C]glucose indicates that, in both the absence and the presence of NH4Cl, the pentose phosphate shunt was only a minor pathway of glucose metabolism. 5. The central role of pyruvate carboxylase in the conversion of glucose carbon into glutamine carbon was demonstrated by using a bicarbonate-free medium and measuring the fixation of 14CO2 from [14C]bicarbonate, which was recovered mostly at C-1 of glutamine plus glutamate. 6. The NH4Cl-induced stimulation of glucose removal was secondary not only to increased glutamine synthesis, as shown by the effect of methionine sulphoximine, an inhibitor of glutamine synthetase, but also to the stimulation of phosphofructokinase activity by NH4Cl. 7. Renal arterio-venous difference measurements revealed that, in vivo, the guinea-pig kidney removed glucose from the circulating blood, which suggests that glucose carbon may contribute to the carbon skeleton of the glutamine released by this organ.

scholarly journals The distinction between γ-glutamylhydroxamate synthetase and l-glutamine–hydroxylamine glutamyltransferase activities in rat tissues. Studies in vitro

1973 ◽  
Vol 133 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Annemarie Herzfeld
Keyword(s):  
Glutamine Synthetase ◽  
Enzyme Activities ◽  
Adenine Nucleotides ◽  
Water Extract ◽  
Rat Tissues ◽  
Synthetase Activity ◽  
Specific Measure ◽  
Glutamine Synthesis ◽  
Methionine Sulphoximine

Two common ways of measuring the potential for glutamine synthesis in a tissue are the rates of formation of γ-glutamylhydroxamate either by synthesis from glutamate (the glutamylhydroxamate synthetase reaction) or by transfer from glutamine (the glutamyltransferase reaction); it has not been established, however, that either reaction is a specific measure of glutamine synthetase. By differential extraction of glutamylhydroxamate synthetase and glutamyltransferase activities from water homogenates of several rat tissues I obtained an extract, rich in glutamylhydroxamate synthetase activity but nearly devoid of glutamyltransferase activity, and a fraction, solubilized by deoxycholate from the pellet, which contained virtually no glutamylhydroxamate synthetase activity but most of the original glutamyltransferase activity. Synthesis of glutamine, quantitatively similar to the γ-glutamylhydroxamate formed by glutamylhydroxamate synthetase, is catalysed in the water extract but not in the particulate fraction. γ-Glutamylhydroxamate formation by glutamylhydroxamate synthetase and glutamyltransferase shows discrepant substrate and metal specificities and can be differentially inhibited by l-methionine sulphoximine, phosphate and adenine nucleotides. The concordance between the formation of glutamine and γ-glutamylhydroxamate by glutamylhydroxamate synthetase but not by glutamyltransferase and the different solubilities of the glutamylhydroxamate synthetase and glutamyltransferase enzyme activities demonstrate that these two activities are not inextricably associated; they therefore cannot be catalysed exclusively by the same protein.

17-Oxidoreduction of 17β-Estradiol, Estrone and Their 3-Sulfates by Kidney Slices from Guinea Pig and Human

1975 ◽  
Vol 53 (12) ◽  
pp. 1333-1336 ◽  
Author(s):  
R. Hobkirk ◽  
Mona Nilsen ◽  
Barbara Jennings
Keyword(s):  
Guinea Pig ◽  
Marked Reduction ◽  
Human Kidney ◽  
Kidney Cortex ◽  
Limited Extent ◽  
Tissue Slices ◽  
Ample Evidence ◽  
Sulfatase Activity ◽  
17Β Estradiol ◽  
Dehydrogenation Reactions

Slices of whole kidney and kidney cortex from the female guinea pig catalyzed a marked reduction of estrone 3-sulfate (E13S) and estrone (E1) to 17β-estradiol 3-sulfate (E23S) and 17β-estradiol (E2), respectively, as well as the reverse (dehydrogenation) reactions. Slices of medulla did not appear active in E23S–E13S interconversion but did possess the ability to interconvert E2 and E1, besides possessing considerable sulfatase activity. The use of [3H-35S]E13S and [3H-35S]E23S as substrates, together with a demonstrated lack of estrogen sulfate synthesis by the tissue slices, provided ample evidence that the intact sulfates were involved in direct oxidoreduction. Slices of human kidney cortex catalyzed the reduction of E13S to a very limited extent. Slices of whole kidney and of cortex from guinea pig formed small amounts of estrogen glucuronide(s).

scholarly journals Proximal tubule-targeted overexpression of the Cyp4a12-20-HETE synthase promotes salt-sensitive hypertension in male mice

2020 ◽  
Vol 319 (1) ◽  
pp. R87-R95
Author(s):  
Ankit Gilani ◽  
Kevin Agostinucci ◽  
Jonathan V. Pascale ◽  
Sakib Hossain ◽  
Sharath Kandhi ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Fold Increase ◽  
High Salt ◽  
Kidney Cortex ◽  
Male Mice ◽  
High Salt Diet ◽  
Salt Diet ◽  
Renal Microvasculature ◽  
Salt Sensitive Hypertension

20-Hydroxyeicosatetraenoic acid (20-HETE) has been linked to blood pressure (BP) regulation via actions on the renal microvasculature and tubules. We assessed the tubular 20-HETE contribution to hypertension by generating transgenic mice overexpressing the CYP4A12-20-HETE synthase (PT-4a12 mice) under the control of the proximal tubule (PT)-specific promoter phosphoenolpyruvate carboxykinase (PEPCK). 20-HETE levels in the kidney cortex of male (967 ± 210 vs. 249 ± 69 pg/mg protein) but not female (121 ± 15 vs. 92 ± 11 pg/mg protein) PT-4a12 mice showed a 2.5-fold increase compared with wild type (WT). Renal cortical Cyp4a12 mRNA and CYP4A12 protein in male but not female PT-4a12 mice increased by two- to threefold compared with WT. Male PT-4a12 mice displayed elevated BP (142 ± 1 vs. 111 ± 4 mmHg, P < 0.0001), whereas BP in female PT-4a12 mice was not significantly different from WT (118 ± 2 vs. 117 ± 2 mmHg; P = 0.98). In male PT-4a12 mice, BP decreased when mice were transitioned from a control-salt (0.4%) to a low-salt diet (0.075%) from 135 ± 4 to 120 ± 6 mmHg ( P < 0.01) and increased to 153 ± 5 mmHg ( P < 0.05) when mice were placed on a high-salt diet (4%). Female PT-4a12 mice did not show changes in BP on either low- or high-salt diet. In conclusion, the expression of Cyp4a12 driven by the PEPCK promoter is sex specific, probably because of its X-linkage. The salt-sensitive hypertension seen in PT-4a12 male mice suggests a potential antinatriuretic activity of 20-HETE that needs to be further explored.

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