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.

Studies on the metabolism of glycolyl-CoA

1990 ◽  
Vol 68 (5) ◽  
pp. 846-851 ◽  
Author(s):  
Joseph Vamecq ◽  
Jacques H. Poupaert
Keyword(s):  
Rat Liver ◽  
Pyruvate Dehydrogenase ◽  
Citrate Synthase ◽  
Rat Kidney ◽  
Kidney Cortex ◽  
Rat Liver Mitochondria ◽  
Succinic Semialdehyde ◽  
Succinic Semialdehyde Dehydrogenase ◽  
Rat Kidney Cortex ◽  
Semialdehyde Dehydrogenase

Glycolyl-CoA can be formed during the course of the β-oxidation by rat liver mitochondria of 4-hydroxybutyrate. The existence of this β-oxidation has been previously supported by the occurrence of 4-hydroxybutyrate and its β-oxidation catabolites in urine from patients with 4-hydroxybutyric aciduria, an inborn error of γ-aminobutyric acid metabolism due to the deficiency of succinic semialdehyde dehydrogenase. The characteristics of the mitochondrial β-oxidation of 4-hydroxybutyrate were, in rat liver, compared with those of the mitochondrial β-oxidation of butyrate. The inhibition by malonate of the oxidation of 4-hydroxybutyrate was about twofold weaker than that of oxidation of butyrate, whereas both oxidations were abolished by preincubating the mitochondria with 1 mM valproic acid, a known inhibitor of mitochondrial β-oxidation. Mitochondria from rat kidney cortex were demonstrated to catalyse, as previously shown for hepatic mitochondria, the carnitine-dependent oxidation of 12-hydroxylauroyl-CoA. ω-Hydroxymonocarboxylyl-CoAs are thus concluded to be precursors of glycolyl-CoA also in rat kidney cortex. In addition, 3-hydroxypyruvate was found to be a precursor of glycolyl-CoA, since it was oxidized by bovine heart pyruvate dehydrogenase with a cofactor requirement similar to that of pyruvate oxidation. Glycolyl-CoA was a substrate of carnitine acetyltransferase (pigeon breast muscle). Pig heart citrate synthase was capable of catalyzing the condensation of glycolyl-CoA with oxaloacetate. The product of this reaction induced low NADH production rates dependent on the addition of porcine heart aconitase and isocitrate dehydrogenase.Key words: glycolyl-CoA, ω-hydroxymonocarboxylates, β-oxidation, 4-hydroxybutyrate, CoA-dependent 3-hydroxypyruvate oxidation, pyruvate dehydrogenase, citrate synthase, hydroxy citrate.

scholarly journals DIRECT COUNTING AND SIZING OF MITOCHONDRIA IN SOLUTION

1972 ◽  
Vol 54 (2) ◽  
pp. 325-345 ◽  
Author(s):  
Adrian R. L. Gear ◽  
Jana M. Bednarek
Keyword(s):  
Electron Microscopy ◽  
Rat Liver ◽  
Rat Kidney ◽  
Mitochondrial Protein ◽  
Kidney Cortex ◽  
Rat Liver Mitochondria ◽  
Particle Volume ◽  
Drug Induced ◽  
Rat Kidney Cortex ◽  
The Mean

Resistive particle counting has been developed for the accurate sizing and counting of mitochondria in solution. The normal detection limit with a 30 µ aperture is 0.48 µ diameter, or 0.056 µ3 particle volume The mean volume of rat liver mitochondria was 0.42 µ3 or 0.93 µ in diameter. The average value for numbers of particles per milligram of mitochondrial protein was 4.3 x 103, and per gram of rat liver was about 11 x 1010. These values compare satisfactorily with those derived by light microscopy and electron microscopy. The mean volume for mitochondria from rat heart was 0 60 µ3 and from rat kidney cortex, 0.23 µ3. These values agree within 15% of those determined by electron microscopy of whole tissue. Mitochondrial fragility and contaminating subcellular organelles were shown to have little influence on the experimentally determined size distributions The technique may be applied to rapid swelling studies, as well as to estimations of the number and size of mitochondria from animals under different conditions such as liver regeneration and hormonal, pathological, or drug-induced states Mitochondrial DNA, RNA, cytochrome c-oxidase, cytochrome (a ÷ a3), and iron were nearly constant per particle over large differences in particle size. Such data may be particularly valuable for biogenesis studies and support the hypothesis that the net amount per particle of certain mitochondrial constituents remains constant during mitochondrial growth and enlargement

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.

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.

scholarly journals The interrelationship of the concentration of hydrogen ions, bicarbonate ions, carbon dioxide and calcium ions in the regulation of renal gluconeogenesis in the rat

1973 ◽  
Vol 136 (3) ◽  
pp. 445-453 ◽  
Author(s):  
George A. O. Alleyne ◽  
Hernando Flores ◽  
Anne Roobol
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Rat Kidney ◽  
Respiratory Acidosis ◽  
Kidney Cortex ◽  
Rat Kidney Cortex ◽  
Bicarbonate Ions ◽  
Cortex Slices ◽  
Glucose Formation ◽  
Kidney Cortex Slices

1. The interrelationship of acidosis and Ca2+on the stimulation of gluconeogenesis by rat kidney-cortex slices was studied. 2. Ca2+stimulated gluconeogenesis from glutamine, glutamate, 2-oxoglutarate, succinate, malate, pyruvate, lactate and fructose, but not from galactose. 3. The [Ca2+] needed for optimum gluconeogenesis was about 2mm, but at this concentration, acidosis, produced in vitro by a decrease of [HCO3−] in the medium at constant pCO2 or by an increase in pCO2 at constant [HCO3−], did not stimulate gluconeogenesis. 4. In the absence of Ca2+, acidosis (low [HCO3−]) stimulated gluconeogenesis from glutamine, glutamate, 2-oxoglutarate, succinate, malate, pyruvate and lactate but not from fructose or galactose. With succinate as substrate, the stimulatory effect of acidosis (low [HCO3−]) disappeared at Ca2+concentrations above 1.0mm. 5. The [HCO3−] was the most important determinant of the acidosis effect since a decrease of pH caused by an increase in pCO2 did not uniformly stimulate gluconeogenesis, whereas a decrease in [HCO3−] without a change in pH consistently stimulated glucose formation in a way similar to the stimulation produced by acidosis (low [HCO3−]) in the absence of Ca2+. 6. Acidosis in vitro inhibited the rate of decrease of activity of phosphoenolpyruvate carboxylase in slices, and Ca2+caused an increase in the activity of fructose 1-phosphate aldolase. 7. Respiratory acidosis in vitro caused an increase in the activity of phosphoenolpyruvate carboxylase in kidney cortex and an increase in gluconeogenesis from glutamine. 8. Possible points of interaction between Ca2+, H+and HCO3−with the gluconeogenic sequence are discussed.

scholarly journals Increase of Na/Pi-cotransport encoding mRNA in response to low Pi diet in rat kidney cortex.

1994 ◽  
Vol 269 (9) ◽  
pp. 6637-6639
Author(s):  
A. Werner ◽  
S.A. Kempson ◽  
J. Biber ◽  
H. Murer
Keyword(s):  
Rat Kidney ◽  
Kidney Cortex ◽  
Rat Kidney Cortex

Cytochrome P-450K of rat kidney cortex microsomes: Further studies on its interaction with fatty acids

1973 ◽  
Vol 158 (2) ◽  
pp. 597-604 ◽  
Author(s):  
Åke Ellin ◽  
Sten Orrenius ◽  
Åke Pilotti ◽  
Carl-Gunnar Swahn
Keyword(s):  
Fatty Acids ◽  
Rat Kidney ◽  
Kidney Cortex ◽  
Rat Kidney Cortex

scholarly journals Studies on the orientation of brush-border membrane vesicles

1978 ◽  
Vol 172 (1) ◽  
pp. 57-62 ◽  
Author(s):  
W Haase ◽  
A Schäfer ◽  
H Murer ◽  
R Kinne
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Rat Kidney ◽  
Freeze Fracture ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles ◽  
Immunological Methods ◽  
Kidney Cortex ◽  
Asymmetric Distribution ◽  
Rat Kidney Cortex

Orientation of rat renal and intestinal brush-border membrane vesicles was studied with two independent methods: electron-microscopic freeze-fracture technique and immunological methods. With the freeze-fracture technique a distinct asymmetric distribution of particles on the two membrane fracture faces was demonstrated; this was used as a criterion for orientation of the isolated membrane vesicles. For the immunological approach the accessibility or inaccessibility of aminopeptidase M localized on the outer surface of the cell membrane to antibodies was used. With both methods we showed that the brush-border membrane vesicles isolated from rat kidney cortex and from rat small intestine for transport studies are predominantly orientated right-side out.

Endogenous Kallikrein Inhibitor in Rat Kidney Cortex-Effect of Glucocorticoid Administration

1986 ◽  
pp. 361-365 ◽  
Author(s):  
Kodo Ito ◽  
Kenichi Yamada ◽  
Setsuko Yoshida ◽  
Keiji Hasunuma ◽  
Yasushi Tamura ◽  
...  
Keyword(s):  
Rat Kidney ◽  
Kidney Cortex ◽  
Rat Kidney Cortex ◽  
Kallikrein Inhibitor ◽  
Glucocorticoid Administration
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