scholarly journals Gluconeogenesis in developing rat kidney cortex

1969 ◽  
Vol 111 (2) ◽  
pp. 181-185 ◽  
Author(s):  
A. Zorzoli ◽  
I. J. Turkenkopf ◽  
V. L. Mueller
Keyword(s):  
Phosphatase Activity ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Rat Kidney ◽  
Maximum Activity ◽  
Kidney Cortex ◽  
Tissue Slices ◽  
Rat Kidney Cortex ◽  
Glucose Synthesis ◽  
Developing Rat ◽  
Glucose Formation

1. Gluconeogenesis in developing rat kidney cortex was studied by assaying the activities of two enzymes, glucose 6-phosphatase and phosphoenolpyruvate carboxykinase, and by measuring glucose formation in tissue slices. 2. Glucose 6-phosphatase and phosphoenolpyruvate carboxykinase are present in late foetal (21–22-day-old) tissue and increase rapidly postnatally. Maximum activity of phosphoenolpyruvate carboxykinase occurs at 7 days of age, followed by a decline to the adult level. Glucose 6-phosphatase activity rises during the first 2 postnatal weeks and then declines. 3. Late foetuses synthesize glucose from both pyruvate and l-glutamate. The rate increases during the first 2 weeks to above adult levels. Synthesis is always higher from pyruvate than from glutamate. 4. The effect of 24hr. starvation was studied in perinatal animals. The results indicate that the ability to increase the rate of glucose synthesis as a result of starvation is not present at birth, but develops some time after the second postnatal day.

Changes in mRNAs for enzymes of glutamine metabolism in kidney and liver during ammonium chloride acidosis

1994 ◽  
Vol 267 (3) ◽  
pp. F400-F406 ◽  
Author(s):  
A. C. Schoolwerth ◽  
P. A. deBoer ◽  
A. F. Moorman ◽  
W. H. Lamers
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Rat Kidney ◽  
Glutamine Metabolism ◽  
Kidney Cortex ◽  
Mrna Levels ◽  
Rat Kidney Cortex ◽  
Physiological Conditions ◽  
Glutamine Synthase ◽  
Sustained Increase

Changes in protein and mRNAs for enzymes of glutamine metabolism were determined in rat kidney cortex at different times after induction of NH4Cl acidosis. After NH4Cl, phosphoenolpyruvate carboxykinase (PEPCK) mRNA increased 16-fold by 10 h (P < 0.05) and then returned to control levels by 30 h. In situ hybridization (ISH) showed that PEPCK mRNA was confined to medullary rays; after NH4Cl, expression of PEPCK expanded throughout the cortex, reaching a maximal intensity at 10 h. Phosphate-dependent glutaminase (PDG) and glutamate dehydrogenase (GDH) mRNAs increased 8- and 2.6-fold, respectively (both P < 0.05), by 10 h before decreasing; the increased expression was confirmed by ISH. Immunohistochemistry showed that increased PEPCK, PDG, and GDH protein occurred at variable times after the rise in mRNAs. The increase was confined to proximal tubules and was sustained, a finding noted also by Western blot analysis. In contrast, glutamine synthase protein and mRNA, confined to deep cortex and outer medullar, did not change after NH4Cl. These studies reveal striking changes in PEPCK and PDG mRNAs in rat renal cortex during acidosis. The ISH pattern suggested that increased amounts of PEPCK were synthesized in recruited cells which contained little enzyme under physiological conditions. mRNA levels for PEPCK, PDG, and GDH peaked at 10 h before returning to control levels. Despite the decrease in mRNAs, a sustained increase in proteins was noted.

scholarly journals Proteomic profiling and pathway analysis of the response of rat renal proximal convoluted tubules to metabolic acidosis

2013 ◽  
Vol 305 (5) ◽  
pp. F628-F640 ◽  
Author(s):  
Kevin L. Schauer ◽  
Dana M. Freund ◽  
Jessica E. Prenni ◽  
Norman P. Curthoys
Keyword(s):  
Metabolic Acidosis ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Pathological Condition ◽  
Rat Kidney ◽  
Proximal Convoluted Tubule ◽  
Kidney Cortex ◽  
Combined Processes ◽  
Proteomic Profiling ◽  
Rat Kidney Cortex ◽  
Cytosolic Proteins

Metabolic acidosis is a relatively common pathological condition that is defined as a decrease in blood pH and bicarbonate concentration. The renal proximal convoluted tubule responds to this condition by increasing the extraction of plasma glutamine and activating ammoniagenesis and gluconeogenesis. The combined processes increase the excretion of acid and produce bicarbonate ions that are added to the blood to partially restore acid-base homeostasis. Only a few cytosolic proteins, such as phosphoenolpyruvate carboxykinase, have been determined to play a role in the renal response to metabolic acidosis. Therefore, further analysis was performed to better characterize the response of the cytosolic proteome. Proximal convoluted tubule cells were isolated from rat kidney cortex at various times after onset of acidosis and fractionated to separate the soluble cytosolic proteins from the remainder of the cellular components. The cytosolic proteins were analyzed using two-dimensional liquid chromatography and tandem mass spectrometry (MS/MS). Spectral counting along with average MS/MS total ion current were used to quantify temporal changes in relative protein abundance. In all, 461 proteins were confidently identified, of which 24 exhibited statistically significant changes in abundance. To validate these techniques, several of the observed abundance changes were confirmed by Western blotting. Data from the cytosolic fractions were then combined with previous proteomic data, and pathway analyses were performed to identify the primary pathways that are activated or inhibited in the proximal convoluted tubule during the onset of metabolic acidosis.

scholarly journals Carbohydrate metabolism of the perfused rat liver

1967 ◽  
Vol 105 (2) ◽  
pp. 869-875 ◽  
Author(s):  
B. D. Ross ◽  
R. Hems ◽  
R. A. Freedland ◽  
H. A. Krebs
Keyword(s):  
Rat Liver ◽  
Rat Kidney ◽  
Kidney Cortex ◽  
Additive Effects ◽  
Perfusion Medium ◽  
Rat Kidney Cortex ◽  
Low Carbohydrate Diet ◽  
Low Carbohydrate ◽  
Glycogen Stores ◽  
Glucose Formation

1. The rates of gluconeogenesis from most substrates tested in the perfused livers of well-fed rats were about half of those obtained in the livers of starved rats. There was no difference for glycerol. 2. A diet low in carbohydrate increased the rates of gluconeogenesis from some substrates but not from all. In general the effects of a low-carbohydrate diet on rat liver are less marked than those on rat kidney cortex. 3. Glycogen was deposited in the livers of starved rats when the perfusion medium contained about 10mm-glucose. The shedding of glucose from the glycogen stores by the well-fed liver was greatly diminished by 10mm-glucose and stopped by 13·3mm-glucose. Livers of well-fed rats that were depleted of their glycogen stores by treatment with phlorrhizin and glucagon synthesized glycogen from glucose. 4. When two gluconeogenic substrates were added to the perfusion medium additive effects occurred only when glycerol was one of the substrates. Lactate and glycerol gave more than additive effects owing to an increased rate of glucose formation from glycerol. 5. Pyruvate also accelerated the conversion of glycerol into glucose, and the accelerating effect of lactate can be attributed to a rapid formation of pyruvate from lactate. 6. Butyrate and oleate at 2mm, which alone are not gluconeogenic, increased the rate of gluconeogenesis from lactate. 7. The acceleration of gluconeogenesis from lactate by glucagon was also found when gluconeogenesis from lactate was stimulated by butyrate and oleate. This finding is not compatible with the view that the primary action of glucagon in promoting gluconeogenesis is an acceleration of lipolysis. 8. The rate of gluconeogenesis from pyruvate at 10mm was only 70% of that at 5mm. This ‘inhibition’ was abolished by oleate or glucagon.

scholarly journals A study of regulation of gluconeogenesis and the supply of cytosolic reducing equivalents for lactate formation in rat kidney-cortical-tubule fragments incubated with pyruvate

1978 ◽  
Vol 174 (1) ◽  
pp. 131-142 ◽  
Author(s):  
E D Saggerson
Keyword(s):  
Steady State ◽  
Cyclic Amp ◽  
Rat Kidney ◽  
Kidney Cortex ◽  
Rat Kidney Cortex ◽  
Fed State ◽  
Lactate Formation ◽  
Energy Dependent ◽  
Glucose Formation ◽  
Reducing Equivalents

1. Tubule fragments were isolated after treatment of rat kidney cortex with collagenase. The formation of glucose and lactate on incubation with 5mM-pyruvate was then measured under various conditions. 2. When tubule fragments were isolated from fed rats in the absence of Ca2+ and then incubated with various Ca2+ concentrations, an incubation period of 15–30 min was necessary to establish a metabolic steady state. Under these conditions glucose formation was increased by Ca2+, adrenaline or 3′:5′-cyclic AMP to a greater extent than was lactate formation. Data show that appreciable lactate formation could not have resulted from glycolytic metabolism of glucose formed by gluconeogenesis during incubation. 3. When tubule fragments were isolated from fed rats in the presence of 1.27 mM-Ca2+ and adjustments made to the Ca2+ concentration at the commencement of incubation, metabolic steady state was rapidly established. Under these conditions lactate formation was almost insensitive to Ca2+ concentration (0.16–4.5 mM), whereas glucose formation varied with Ca2+ concentration in a sigmoidal manner. 3′:5′-Cyclic AMP decreased this sigmoidicity. 4. Ca2+ depletion of the tissue before incubation appeared to change permanently the relationship between extracellular Ca2+ concentration and the measured rates of metabolic processes. 5. Under conditions of metabolic steady state, glucose formation by tubule fragments from fed rats was less sensitive than lactate formation to inhibition by 3-mercaptopicolinate or 2-n-butylmalonate. Lactate formation by tubule fragments prepared from 48 h-starved rats was more sensitive to these inhibitors. 6. Estimates were made of the rate of futile cycling of C3 species through pyruvate kinase. This was greater in the starved than in the fed state, was decreased by 3′:5′-cyclic AMP in both the fed and the starved state, but was unaffected by Ca2+. 7. These results suggested that formation of lactate and glucose is less tightly linked in kidney cortex than in liver. A considerable amount of the supply of reducing equivalents for lactate formation did not appear to be associated with an energy-dependent translocation from mitochondria to cytosol involving a pyruvate leads to oxaloacetate leads to phosphoenolpyruvate leads to pyruvate cycle.

DDT-Induced Stimulation of Key Gluconeogenic Enzymes In Rat Kidney Cortex

1972 ◽  
Vol 50 (2) ◽  
pp. 225-229 ◽  
Author(s):  
S. Kacew ◽  
R. L. Singhal ◽  
G. M. Ling
Keyword(s):  
Pyruvate Carboxylase ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Rat Kidney ◽  
Kidney Cortex ◽  
Glucocorticoid Hormones ◽  
Rat Kidney Cortex ◽  
Gluconeogenic Enzymes ◽  
Maximal Stimulation ◽  
Adrenalectomized Rats ◽  
Stimulation Of

Administration of technical DDT or o,p′-DDT produced marked increases in pyruvate carboxylase, phosphoenolpyruvate carboxykinase, fructose-1,6-diphosphatase, and glueose-6-phospfaatase activities in rat kidney cortex. Significant increases in these key gluconeogenic enzymes occurred at 2–3 days and maximal stimulation was seen 5–7 days after the beginning of o,p′-DDT treatment. This DDT isomer, when given to adrenalectomized rats, produced increases in renal enzymes similar to those observed in intact animals. Furthermore, since administration of triamcinolone to o,p′-DDT-treated rats failed to potentiate the action of this insecticide on various enzymes, evidence indicates that the stimulation of kidney cortex gluconeogenesis by DDT is not mediated through a release of glucocorticoid hormones from the adrenal cortex.

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