Localization and role of pyruvate kinase isoenzymes in the regulation of carbohydrate metabolism and pyruvate recycling in rat kidney cortex

1. The role of Ca2+ in the control of renin release was investigated using a collagenase-dispersed rat kidney cortex cell preparation. 2. Superfusion with a series of low [Ca2+] buffers in either ascending or descending order of concentration increased renin release. Exposure to 0.06 mmol/l Ca2+ increased release by 120% (P < 0.001) when presented as the first buffer in ascending order of concentration and by 79% (P < 0.001) when presented as the fourth and last in a series of descending order. 3. The Ca2+ entry blocking drug diltiazem in a range of concentrations increased renin release and at 10−5 mol/l diltiazem the mean stimulation was 35% (P < 0.01). 4. 8-(N,N-Diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) reduces the release of Ca2+ from intracellular stores and, studied over a range of concentrations, this compound increased renin release. At 10−5 mol/l TMB-8 the mean increase was 44% (P < 0.001). 5. None of these experimental manipulations, low [Ca2+], diltiazem or TMB-8, had any effect on the release of adenosine 3′:5′-cyclic monophosphate into the cell superfusate, indicating that a decrease in intracellular [Ca2+] increases renin release by a mechanism which is independent of changes in adenosine 3′:5′-cyclic monophosphate production. 6. Effects of low [Ca2+], diltiazem and TMB-8 on renin secretion were all shown to be reversible when superfusion with control buffer was resumed.

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Effect of bicarbonate on glutamine and glutamate metabolism by rat kidney cortex mitochondria

AJP Renal Physiology ◽

10.1152/ajprenal.1985.249.4.f573 ◽

1985 ◽

Vol 249 (4) ◽

pp. F573-F581

Author(s):

R. C. Scaduto ◽

A. C. Schoolwerth

Keyword(s):

Rat Kidney ◽

Competitive Inhibitor ◽

Kidney Cortex ◽

Mitochondrial Enzymes ◽

Glutamate Metabolism ◽

Bicarbonate Buffer ◽

Rat Kidney Cortex ◽

Glutamate Oxalacetate Transaminase ◽

Stimulation Of

Isolated rat kidney cortex mitochondria were incubated at pH 7.4 in the presence or absence of a CO2/bicarbonate buffer (28 mM) to investigate the pH-independent role of bicarbonate on glutamine and glutamate metabolism. Changes in the concentration of key intermediates and products during the incubations were used to calculate metabolite flux rates through specific mitochondrial enzymes. With 1 mM glutamine and 2 mM glutamate as substrates, bicarbonate caused an inhibition of glutamate oxalacetate transaminase flux and a stimulation of glutamate deamination. The same effects were also produced with addition of either aminooxyacetate or malonate. These effects of bicarbonate were prevented when 0.2 mM malate was included as an additional substrate. Bicarbonate ion was identified as a potent competitive inhibitor of rat kidney cortex succinate dehydrogenase. These results indicate that aminooxyacetate, malonate, and bicarbonate all act to stimulate glutamate deamination through a suppression of glutamate transamination, and that the control by transamination of glutamate deamination is due to alterations in alpha-ketoglutarate metabolism. In contrast, in mitochondria incubated with glutamine in the absence of glutamate, bicarbonate was found to inhibit glutamate dehydrogenase flux. This effect was found to be due in part to the lower intramitochondrial pH observed in incubations with bicarbonate. These findings indicate that bicarbonate ion, independent of pH, may have an important regulatory role in renal glutamine and glutamate metabolism.

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PPARα Gene Expression in the Developing Rat Kidney: Role of Glucocorticoids

Journal of the American Society of Nephrology ◽

10.1681/asn.v1261197 ◽

2001 ◽

Vol 12 (6) ◽

pp. 1197-1203

Author(s):

FATIMA DJOUADI ◽

JEAN BASTIN

Keyword(s):

Gene Expression ◽

Fatty Acids ◽

Fatty Acid ◽

Culture Media ◽

Rat Kidney ◽

Fold Increase ◽

Kidney Cortex ◽

Peroxisome Proliferator ◽

Rat Kidney Cortex

Abstract. The α isoform of peroxisome proliferator-activated receptor (PPARα), which is highly expressed in the kidney, can stimulate the expression of genes that are involved in fatty acid catabolism and therefore might be involved in the control of renal fatty acid β-oxidation. PPARα expression and its regulation in the immature kidney are not well documented. This study delineated the developmental pattern of PPARα expression in the rat kidney cortex and the medulla between postnatal days 10 and 30 and investigated the role of glucocorticoids in regulating PPARα expression. In the cortex, PPARα mRNA and protein increased 2- and 1.8-fold, respectively, from 10 to 21 d and then decreased 1.5- and 2.4-fold from 21 to 30 d. In the medulla, PPARα mRNA and protein increased continuously 3.3- and 2.4-fold, respectively. It is shown here that acute treatment by dexamethasone of 10-d-old rats precociously induced a 4- to 6-fold increase in PPARα mRNA and a 1.8-fold increase in protein within 6 h in each part of the kidney. Chronic injection of dexamethasone for 3 d also increased PPARα mRNA 3.8- and 2.2-fold in the cortex and the medulla, respectively, with a 1.5- and 2-fold increase in protein. Furthermore, adrenalectomy prevented the increases in PPARα mRNA and protein in both the cortex and the medulla between postnatal days 16 and 21, and these could be restored by dexamethasone treatment. Finally, with the use of an established renal cell line, it was shown that glucocorticoids stimulate gene expression of PPARα and of medium chain acyl-CoA dehydrogenase (MCAD, a PPARα target gene) 2- to 4-fold and 1.5-fold, respectively, and that addition of fatty acids in the culture media led to a 2.2-fold increase in MCAD mRNA. Altogether, these results demonstrated that glucocorticoids are potent regulators of PPARα development in the immature kidney and that these hormones act in concert with fatty acids to regulate MCAD gene expression in renal cells.

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The regulation of phosphoenolpyruvate carboxykinase (GTP) synthesis in rat kidney cortex. The role of acid-base balance and glucocorticoids.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)41221-0 ◽

1975 ◽

Vol 250 (14) ◽

pp. 5596-5603

Author(s):

P B Iynedjian ◽

F J Ballard ◽

R W Hanson

Keyword(s):

Phosphoenolpyruvate Carboxykinase ◽

Rat Kidney ◽

Kidney Cortex ◽

Acid Base Balance ◽

Acid Base ◽

Rat Kidney Cortex ◽

Base Balance

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Role of Fatty Acids in Simultaneous Regulation of Flux Through Glutaminase and Glutamine Synthetase in Rat Kidney Cortex

Glutamine Metabolism in Mammalian Tissues ◽

10.1007/978-3-642-69754-8_12 ◽

1984 ◽

pp. 187-202 ◽

Cited By ~ 6

Author(s):

G. Baverel ◽

C. Michoudet ◽

G. Martin

Keyword(s):

Fatty Acids ◽

Glutamine Synthetase ◽

Rat Kidney ◽

Kidney Cortex ◽

Rat Kidney Cortex

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Effects of added adenine nucleotides on renal carbohydrate metabolism

Biochemical Journal ◽

10.1042/bj1150001 ◽

1969 ◽

Vol 115 (1) ◽

pp. 1-10 ◽

Cited By ~ 26

Author(s):

M. J. Weidemann ◽

D. A. Hems ◽

H. A. Krebs

Keyword(s):

Glucose Uptake ◽

Carbohydrate Metabolism ◽

Adenine Nucleotides ◽

Rat Kidney ◽

Kidney Cortex ◽

Rat Kidney Cortex ◽

Isolated Perfused Rat Kidney ◽

Perfused Rat Kidney ◽

Cortex Slices ◽

Kidney Cortex Slices

1. The regulatory effects that adenine nucleotides are known to exert on enzymes of glycolysis and gluconeogenesis were demonstrated to operate in kidney-cortex slices and in the isolated perfused rat kidney by the addition of exogenous ATP, ADP and AMP to the incubation or perfusion media. 2. Both preparations rapidly converted added ATP into ADP and AMP, and ADP into AMP; added AMP was rapidly dephosphorylated. AMP formed from ATP was dephosphorylated at a lower rate than was added AMP, especially when the initial ATP concentration was high (10mm). Deamination of added AMP occurred more slowly than dephosphorylation of AMP. 3. Gluconeogenesis from lactate or propionate by rat kidney-cortex slices, and from lactate by the isolated perfused rat kidney, was inhibited by the addition of adenine nucleotides to the incubation or perfusion media. In contrast, oxygen consumption and the utilization of propionate or lactate by slices were not significantly affected by added ATP or AMP. 4. The extent and rapidity of onset of the inhibition of renal gluconeogenesis were proportional to the AMP concentration in the medium and the tissue, and were not due to the production of acid or Pi or the formation of complexes with Mg2+ ions. 5. Glucose uptake by kidney-cortex slices was stimulated 30–50% by added ATP, but the extra glucose removed was not oxidized to carbon dioxide and did not all appear as lactate. Glucose uptake, but not lactate production, by the isolated perfused kidney was also stimulated by the addition of ATP or AMP. 6. In the presence of either glucose or lactate, ATP and AMP greatly increased the concentrations of C3 phosphorylated intermediates and fructose 1,6-diphosphate in the kidney. There was a simultaneous rise in the concentration of malate and fall in the concentration of α-oxoglutarate. 7. The effects of added adenine nucleotides on renal carbohydrate metabolism seem to be mainly due to an increased concentration of intracellular AMP, which inhibits fructose diphosphatase and deinhibits phosphofructokinase. This conclusion is supported by the accumulation of intermediates of the glycolytic pathway between fructose diphosphate and pyruvate. 8. ATP or ADP (10mm) added to the medium perfusing an isolated rat kidney temporarily increased the renal vascular resistance, greatly diminishing the flow rate of perfusion medium for a period of several minutes.

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Presence and possible role of a renal brush-border Gly-Pro-X-releasing exopeptidase

AJP Renal Physiology ◽

10.1152/ajprenal.1987.253.4.f649 ◽

1987 ◽

Vol 253 (4) ◽

pp. F649-F655

Author(s):

Knut-Jan Andersen ◽

J. Ken McDonald

Keyword(s):

Brush Border ◽

Rat Kidney ◽

Kidney Cortex ◽

Membrane Domains ◽

Rat Kidney Cortex ◽

Proximal Tubule Cells ◽

Dpp Iv ◽

Tripeptidyl Peptidase ◽

Membrane Compartment

Differential pelleting of a rat renal cortical homogenate clearly demonstrated the microsomal localization of an N-terminal exopeptidase of the tripeptidyl peptidase (TPP) class that typically requires a free N-terminus to catalyze the release of collagen-related (Gly-Pro-X) “triplets” at pH 7.0 (TPP 7). Once fractionated by differential pelleting, microsomal populations of different size were subfractionated by equilibrium banding in sucrose gradients for the purpose of comparing the distribution profiles and the isopycnic banding densities of TPP 7 to those for known marker enzymes. This analytical approach permitted the localization of these enzymes to specific membrane domains in the renal cortex and provided evidence for the brush-border location of TPP 7. Notably, dipeptidyl peptidase IV (DPP IV), an established plasma membrane exopeptidase with a prolyl-bond specificity, gave banding densities and distributions that were consistent with the presence of both TPP 7 and DPP IV in the same membrane compartment. Because triplets of the Gly-Pro-X type released by TPP 7 would be ideal substrates for DPP IV, a coupled TPP 7-DPP IV exopeptidase mechanism at the luminal surface (brush border) of proximal tubule cells could therefore make a major contribution to the renal degradation and reabsorption of filtered collagen fragments. tripeptidyl peptidase; aminopeptidase; collagen; rat kidney cortex Submitted on February 11, 1987 Accepted on May 13, 1987

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