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Hemodynamic and metabolic characteristics of an isolated guinea pig heart preparation perfused with a pyruvate fortified Krebs-Ringer-bicarbonate solution are described. The preparation is stable for more than 90 min with respect to coronary flow, heart rate, left ventricular pressure, dP/dt, oxygen consumption, and myocardial high energy phosphate levels. The changes in coronary flow induced by alterations of perfusion pressure, ischemia, and hypoxia resemble those seen under in vivo conditions. The preparation also exhibits concentration dependent and reproducible changes in coronary resistance upon administration of adenosine and papaverine. The in vivo like features of this preparation can be mainly attributed to the use of pyruvate as additional and preferentially utilized substrate. The preparation appears to be suitable for quantitative studies of myocardial metabolism and heart function as well as for investigations of the coronary system. [ABSTRACT FROM AUTHOR]

A non-recirculating, haemoglobin-free perfusion system was used to evaluate glycolysis in livers from fasted rats. Glycolysis was calculated from lactate and pyruvate production before and after infusion of glucose. In the absence of extracellular glucose glycolysis was small. Stimulation of glycolytic flux occured at extracellular glucose concentrations above 5 mM. Rates were proportional to glucose concentrations. Glycolysis was also investigated in the presence of extracellular lactate, which is a precursor of gluconeogenesis. High glucose concentrations (15-35 mM) were followed by lactate and pyruvate output suggesting that glycolysis was prevailing. Estimated flux rates, however, were significantly lower in the presence of the gluconeogenic precursor. Our results provide arguments that gluconeogenesis and glycolysis interact in order to regulate the peripheral glucose concentration. [ABSTRACT FROM AUTHOR]

Thyroxine treatment increases blood glucose and plasma insulin levels in the rat. The hypoglycemic effect of tolbutamide is more pronounced in treated animals. The immediate insulin secretory response of the isolated perfused pancreas to maximal, but not to submaximal, glucose stimuli was increased after thyroxine treatment, especially in the lower dose range. However, as thyroxine treatment reduces insulin release during the prolonged late phase, the total amount of insulin released from the pancreas is reduced. Both the early response to tolbutamide and the subsequent basal secretion were increased after thyroxine treatment. When the pancreas of treated rats was exposed to glucose plus pyruvate the inhibition of the late phase was reversed. Isoprenaline did not overcome the inhibitory effect of thyroxine treatment on the late phase of glucose-induced insulin release. Thyroxine induces a selective inhibition of glucose induced insulin release which is reversed by pyruvate; this indicates that thyroxine interferes with the glycolysis in the beta cell. [ABSTRACT FROM AUTHOR]

The fermatation metabolism of Rhodospirillum rubrum Ha was studied after adaptation of both light-anaerobic and dark aerobic to dark anaerobic conditions. Pyruvate was metabolized to acetate, formate, CO and propionate by suspensions of cells adapted to anaerobiosis. Pyruvate cleavage to formate accounted for about two-thirds of the pyruvate decomposed. This process was catalyzed by a coenzyme A dependent pyruvate formate lyase. In carboxylate- and nucleotide-free extracts, the substrate concentrations for half-maximal velocity [S] were found to be 1.5 mM for pyruvate and 75 μM for coenzyme A. Pyruvate formate lyase could practically not be demonstrated in light-anaerobic photosynthesizing cells. Lyase activity was low at a 'basic' level in darkaerobic respiring cells. After adaptation of both types of cells under growth conditions to dark anaerobiosis lyase activity increased about 10-fold. Highest levels could be observed in cells grown aerobically in the dark on pyruvate after transition to dark anaerobic conditions. It is concluded that pyruvate formate lyase is the characteristic key enzyme of the dark-anaerobic fermentative metabolism of R. rubrum Ha. [ABSTRACT FROM AUTHOR]

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RQ, plasma insulin, blood glucose, lactate and pyruvate were measured in six fit, normal subjects during a series of exercise and rest experiments with and without sucrose ingestion. Subjects exercised on a bicycle ergometer for 50 min of every hour for 6 h at about 47% of the group's average maximal aerobic capacity. In the resting experiments, the subjects sat for 6 h in an armchair. A solution containing 100 g of sucrose was ingested at the beginning of the fourth hour during the sucrose experiments. Ingestion of sucrose caused a significant increase in RQ, plasma insulin, blood glucose, lactate and pyruvate in both exercise and rest experiments. Insulin, lactate and pyruvate concentrations rose higher during rest after sucrose ingestion than during exercise. The time courses of the changes in RQ, insulin, glucose, lactate and pyruvate after sucrose ingestion, suggest that glucose entering the cell during rest is immediately oxidized, while during work there is some delay in the oxidation of glucose. [ABSTRACT FROM AUTHOR]

The concentration of lactate and pyruvate in arterial and in venous blood draining a resting limb were determined in seven young adults at rest, during and after exercise and after injection of sodium-( l+)-lactate. The results exclude the concept that the elevated lactate/pyruvate ratio in arterial blood during exercise originates in the resting extremities, and suggest that the lactate/pyruvate ratio in the blood is of limited value as an indicator of the cellular redox level in muscle. [ABSTRACT FROM AUTHOR]

Four well-trained male subjects worked for periods of 6 h on bicycle ergometers at work loads requiring about 47% of their maximal aerobic capacity. In one series of studies they received only water; in a second series they received 100 g of sucrose containing 100 μc U-C-labelled sucrose at the beginning of the fourth hour of work. In a third series of experiments, the same subjects received 100 g of non-labelled sucrose at the beginning of the fourth hour. During the experiment without U-C-labelled sucrose, blood samples were withdrawn and analysed for glucose, lactate and pyruvate content. Data from CO recovery in expired air showed a good correlation with the amount of carbohydrate oxidized during the sucrose experiment. Peak values for the respiratory exchange ratio showed the same time response as those observed for the CO in the expired air. It is concluded that the observed rise in RQ after sucrose ingestion, under the conditions studied, is of metabolic origin, resulting from a complete conversion of pyruvate to CO. [ABSTRACT FROM AUTHOR]

It has been shown in a previous paper that the temperature has a marked eflect on the intracellular pH. It was suggested that a shift from organic to inorganic phosphate compounds and changes in the NAD/NADH system possibly account for this effect. To test this hypothesis lactate, pyruvate, total phosphate, ATP, creatin phosphate and inorganic phosphate of skeletal muscle were determined in anaesthetized rats at a body temperature of 39.6 or 24.6°C. The artificial ventilation was kept constant. At the low temperature $$P_{{\text{CO}}_{\text{2}} }$$ was lower and pH higher than at a normal temperature. There was no gross change, however, in the OH/H ratio. Neither the lactate/pyruvate ratio nor the phosphate compounds were affected by hypothermia. The effect of temperature on the intracellular pH therefore cannot be explained by changes in the intracellular phosphate compounds or by changes in the NAD/NADH system. [ABSTRACT FROM AUTHOR]

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Copyright of Acta Diabetologica Latina is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The following parameters have been determined in anesthetized dogs: Urine volume (UV), GFR, renal blood flow (RBF), sodium excretion (E), tubular sodium reabsorption (T), the arterial and renal venous concentration, a- v difference and renal net uptake of glucose, lactate, pyruvate, and nonesterified fatty acids (FFA). After control periods, 5 mg/kg furosemide or ethacrynic acid have been injected intravenously. Tissue concentrations of glycogen in cortex and medulla have been compared before and after administration of the two diuretics. Both, furosemide and ethacrynic acid had comparable effects on UV, GFR, E and T at the doses given. The mean increase of RBF was 34% after ethacrynic acid and 23% after furosemide. The net uptake of the substrates in 68 control measurements in 17 dogs averaged 60.0±6.2 for lactate, 5.0±0.8 for pyruvate and 15.0±2.1 for FFA (μmol/min · 100 g kidney weight). The correlation of arterial load and net uptake was significant for lactate and FFA. In- and outflow of glucose were not significantly different. There was no net uptake of glucose even after a 4-5 fold increase of the arterial concentration by an i.v. infusion of glucose. Neither furosemide nor ethacrynic acid had an effect on renal glucose balance. Both blocked the renal uptake of FFA completely. After furosemide the uptake of lactate and pyruvate averaged only about one half of the respective controls whereas there was a net release of both substrates after ethacrynic acid. The glycogen concentration of the renal cortex amounted to 0.48 mmol glucose/kg wet weight in renal cortex and to 1.40 in medulla. Both diuretics increased tissue glycogen concentration by 20-25%. One can conclude that both, furosemide and ethacrynic acid, inhibit the oxidative metabolism in renal cortex whereas anaerobic glycolysis is less or not affected. The results are discussed with regard to the constant oxygen consumption which has been observed in previous experiments. [ABSTRACT FROM AUTHOR]

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Fatty acid synthesis in adipose tissue normally proceeds at a high rate when fasted animals are refed a diet containing carbohydrate, protein, and low levels of fat. This study investigated the effect of omitting protein from the refeeding diet.Rats were fasted for 48 hr and refed either a protein-free diet or a balanced diet, and the rate of fatty acid synthesis from glucose, pyruvate, lactate, and aspartate was measured. Refeeding the animals a diet devoid of protein resulted in a low rate of fatty acid synthesis from each of these substrates as well as a reduction in carbon flow over the citrate cleavage pathway. The activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, NADP-malate dehydrogenase, and ATP-citrate lyase were also reduced in epididymal fat pads from these rats. On the other hand, adipose tissue phosphoenolpyruvate carboxykinase activity was five times as great as that in tissue from animals refed a balanced diet. This difference could be eliminated if actinomycin D was injected coincident with refeeding.Refeeding rats diets high in carbohydrate is not, therefore, capable of inducing high rates of fatty acid synthesis in adipose tissue in the absence of dietary proteins. Thus, liver and adipose tissue respond differently to dietary protein.

Aim. To assess antioxidant system (AOS) enzyme activity and red blood cell hypoxia severity, according to compensatory-adaptive reaction type in young men with mitral valve prolapse (MVP). Material and methods. In 137 young men with MVP, red blood cell activity of catalase (C), glutathione reductase (GR), superoxide dismutase (SOD), lactate, pyruvate concentration, lactate/pyruvate (L/P) coefficient were measured by standard methods, together with cardiohemodynamic parameters. Results. In Group I (high compensatory-adaptive potential), L/P was 2,2 times higher than in controls. In Group II (decreased compensatory-adaptive potential), this parameter was higher than in controls by 14,6% (p

Commercial serum albumin was found to contain lactate, pyruvate, and especially citrate in addition to fatty acids. Glucose, aspartate, and α-ketoglutarate were also present but at lower concentrations. Charcoal treatment followed by prolonged dialysis was effective in removing most of these contaminants.