Anaerobic Rat Heart: Effect of Glucose and Krebs Cycle Metabolites on Rate of Beating

1968 ◽  
Vol 127 (1) ◽  
pp. 25-30 ◽  
Author(s):  
J. Cascarano ◽  
W. L. Chick ◽  
I. Seidman
Keyword(s):  
Rat Heart ◽  
Krebs Cycle ◽  
Effect Of Glucose

Computer simulation of metabolism in pyruvate-perfused rat heart. II. Krebs cycle

1979 ◽  
Vol 237 (3) ◽  
pp. R159-R166 ◽  
Author(s):  
M. C. Kohn ◽  
M. J. Achs ◽  
D. Garfinkel
Keyword(s):  
Redox Potential ◽  
Rat Heart ◽  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Krebs Cycle ◽  
Coordinated Control ◽  
Work Load ◽  
Metabolic Model ◽  
Tricarboxylic Acid ◽  
Perfused Rat Heart

A realistic metabolic model of the tricarboxylic acid cycle in the perfused rat heart was constructed to help explain the sequence of biochemical events regulating the metabolism of exogenous pyruvate following a large increase in work load. The unchelated Mg2+ level was the most important controlling factor. The resulting mixture of chelated and unchelated nucleotides and tribasic acids effected coordinated control of citrate synthase, aconitase, isocitrate dehydrogenase, succinyl CoA synthetase, fumarase, and nucleoside diphosphokinase, because Mg2+-chelates are generally substrates whereas unchelated species are inhibitors. Succinate dehydrogenase is largely controlled by the ubiquinone redox potential. The fluxes through alpha-ketoglutarate and malate dehydrogenases are largely dependent on thepyridine nucleotide redox potential, but the succinyl CoA-to-CoASH ratio strongly affects the former enzyme as well. The model predicts an accumulation of succinate during the transition to higher work output.

Computer simulation of energy metabolism in anoxic perfused rat heart

1977 ◽  
Vol 232 (5) ◽  
pp. R164-R174 ◽  
Author(s):  
M. J. Achs ◽  
D. Garfinkel
Keyword(s):  
Energy Metabolism ◽  
Rat Heart ◽  
Krebs Cycle ◽  
Control Mechanisms ◽  
Transport Mechanisms ◽  
Perfused Rat Heart ◽  
Rate Laws ◽  
Data Requirements ◽  
Physiological And Biochemical

We have modeled the energy metabolism of the perfused rat heart in order to elucidate the interaction of physiological and biochemical control mechanisms. This model which includes glycolysis, the Krebs cycle, and related metabolism, contains 68 submodels of individual enzymes and transport mechanisms including both cytosolic and mitochondrial reactions. The method of model construction, which relies heavily on fitting observed in situ behavior to known algebraic rate laws for isolated enzymes, and its data requirements and necessary assumptions are described. Simulation of a CO-induced anoxic preparation is described in detail. Here glycolysis increases sharply, due to both increased glucose uptake and phosphorylase activation (there is rapid interconversion between a and b forms, both of which are active here); this causes a damped glycolytic oscillation originating with the glycogen-handling enzymes rather than phosphofructokinase. The behavior and physiological consequences of ATPase activity and of a lactate permease which exports lactate to the perfusate are discussed.

ATP-Citrate Lyase Localized with the Peroxidase-Antiperoxidase Technique in RAT Heart and Liver

1982 ◽  
Vol 40 ◽  
pp. 40-41
Author(s):  
W.A. Shannon ◽  
C.S. Chang ◽  
S.B. Bates
Keyword(s):  
Rat Heart ◽  
Kinetic Data ◽  
Krebs Cycle ◽  
Enzyme Kinetic ◽  
Atp Citrate Lyase ◽  
Macromolecular Complexes ◽  
Citrate Lyase ◽  
Cleavage Enzyme ◽  
Soluble Enzymes

Enzyme kinetic data has indicated the probability of “soluble” enzymes existing in situ as macromolecular complexes. These enzymes often function in sequential reactions, e. g., mitochondrial Krebs cycle. Therefore, it is important to define morphologically their functional in situ localization. One such enzyme of interest is ATP-citrate lyase (citrate cleavage enzyme). Biochemically, it has been characterized as a cytoplasmic enzyme. However, there are teleological as well as other indications that it may be concentrated in the vicinity of mitochondria.

An Attempt at the Cytochemical Localization of Citrate Synthase in Rat Heart Muscle

1976 ◽  
Vol 34 ◽  
pp. 86-87 ◽  
Author(s):  
M. A. Matlib ◽  
W. A. Shannon ◽  
P. A. Srere
Keyword(s):  
Heart Muscle ◽  
Rat Heart ◽  
Citrate Synthase ◽  
Krebs Cycle ◽  
Model Systems ◽  
Soluble Form ◽  
Cytochemical Localization ◽  
Inner Membrane ◽  
Membrane Area ◽  
Krebs Cycle Enzymes

Most of the Krebs cycle enzymes are believed to exist in ‘soluble’ form in the mitochondrial matrix except succinate dehydrogenase which is a part of the inner membrane (1). Citrate synthase, one of the Krebs cycle enzymes, is present in rat liver, kidney and heart mitochondria proportional to the amount of the inner membrane area rather than the matrix volume (2). Recent studies on model systems support the idea that the ‘soluble’ Krebs cycle enzymes are probably localized on the inner surface (matrix side) of the inner membrane (3-5). Localization of these enzymes in mitochondria by cytochemical or immunocytochemical methods would be crucial to determine the validity of the above hypothesis. The present study describes cytochemical localization of citrate synthase in rat heart muscle.

Effect of glucose on potassium contracture tension in rat heart

Life Sciences ◽  
1973 ◽  
Vol 13 (5) ◽  
pp. 441-451 ◽  
Author(s):  
David A. Berman
Keyword(s):  
Rat Heart ◽  
Potassium Contracture ◽  
Effect Of Glucose

scholarly journals Glycolytic and oxidative metabolism in relation to retinal function.

1981 ◽  
Vol 77 (6) ◽  
pp. 667-692 ◽  
Author(s):  
B S Winkler
Keyword(s):  
Glucose Concentration ◽  
Krebs Cycle ◽  
Lactate Production ◽  
Optimal Level ◽  
High Rate ◽  
Atp Content ◽  
Isolated Retina ◽  
Effect Of Glucose ◽  
Aerobic And Anaerobic

Measurements of lactate production and ATP concentration in superfused rat retinas were compared with extracellular photoreceptor potentials (Fast PIII). The effect of glucose concentration, oxygen tension, metabolic inhibition, and light were studied. Optimal conditions were achieved with 5-20 mM glucose and oxygen. The isolated retina had a high rate of lactate production and maintained the ATP content of a freshly excised retina, and Fast PIII potentials were similar to in vivo recordings. Small (less than 10%) decreases in aerobic and anaerobic lactate production were observed after illumination of dark-adapted retinas. There were no significant differences in ATP content in dark- and light-adapted retinas. In glucose-free medium, lactate production ceased, and the amplitude of Fast PIII and the level of ATP declined, but the rates of decline were slower in oxygen than in nitrogen. ATP levels were reduced and the amplitude of Fast PIII decreased when respiration was inhibited, and these changes were dependent on glucose concentration. Neither glycolysis alone nor Krebs cycle activity alone maintained the superfused rat retina at an optimal level. Retinal lactate production and utilization of ATP were inhibited by ouabain. Mannose but not galactose or fructose produced lactate and maintained ATP content and Fast PIII. Iodoacetate blocked lactate production and Fast PIII and depleted the retina of ATP. Pyruvate, lactate, and glutamine maintained ATP content and Fast PIII reasonably well (greater than 50%) in the absence of glucose, even in the presence of iodoacetate. addition of glucose, mannose, or 2-deoxyglucose to medium containing pyruvate and iodoacetate abolished Fast PIII and depleted the retina of its ATP. It is suggested that the deleterious effects of these three sugars depend upon their cellular uptake and phosphorylation during the blockade of glycolysis by iodoacetate.

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