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Query: UMLS:C0003129 (Anoxia)
 551 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Effects of glucose concentration and anoxia upon the metabolite concentrations and rates of glycolysis and respiration have been investigated in the perfused liver of the fetal guinea pig. In most cases the metabolite concentrations in the perfused liver were similar to those observed in vivo. Between 50 days and term there was a fall in the respiratory rate and in the concentration of ATP and fructose 1,6-diphosphate and an increase in the concentration of glutamate, glycogen and glucose. Reducing the medium glucose concentration from 10 mM to 1 mM or 0.1 mM depressed lactate production and the concentration of most of the phosphorylated intermediates (except 6-phosphogluconate) in the liver of the 50-day fetus. This indicates a fall in glycolytic rate which is not in accord with the known kinetic properties of hexokinase in the fetal liver. Anoxia increased lactate production by, and the concentrations of, the hexose phosphates ADP and AMP in the 50-day to term fetal liver, while the concentration of ribulose 5-phosphate, ATP and some triose phosphates fell. These results are consistent with an activation of glycolysis, particularly at phosphofructokinase and of a reduction in pentose phosphate pathway activity, particularly at 6-phosphogluconate dehydrogenase. The calculated cytosolic NAD+/NADH ratio for the perfused liver was similar to that measured in vivo and evidence is presented to suggest that the dihydroxyacetone phosphate/glycerol 3-phosphate ratio gives a better indication of cytosolic redox than the lactate/pyruvate ratio. The present observations indicate that phosphofructokinase hexokinase and possibly pyruvate kinase control the glycolytic rate and that glyceraldehyde-3-phosphate dehydrogenase is at equilibrium in the perfused liver of the fetal guinea pig.
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PMID:Some effects of glucose concentration and anoxia on glycolysis and metabolite concentrations in the perfused liver of fetal guinea pig. 2 74

1. The effects of monosaccharides, glycolytic intermediates, metabolic inhibitors and anxia, have been studied on the membrane electrical activity of mouse pancreatic islet cells in vitro using a single intracellular micro-electrode for both voltage recording and current injection. 2. In addition to D-glucose (28mM), D-mannose (16-6mM), and L-leucin (10mM), the substances D-glyceraldehyde (11mM), and acetoacetate (20 mM), induced action potentials in islet cells but other glucos analogues and metabolic intermediates including L-glucose dod not. 3. Mannoheptulose 20 mM), but not D-galactose or 2-deoxy-D-glucose, antagonized the electrical activity induced in islet cells by D-glucose, 28mM. Prior treatment of the cells with mannoheptulose caused them to hyperpolarize and completely prevented the appearance of electrical activity on subsequent exposure to D-glucose. 4. Electrical activity induced by D0glucose 28mM, was progressively inhibited by phloridzin, 10mM, if the cells were exposed to D-glucose and inhibitor simultaneously, and abolished on pretreatment with inhibitor for 30-60 min. Phloridzin also caused depolarization of the islet cells which was independent of extracellular glucose. 5. Anoxia completely blocked the electrical activity induced by glucose but not that evoked by D-glyceraldehyde, L-leucine, tolbutamide or glibenclamide. 6. Iodoacetic acid, 5 mM, rapidly blocked glucose-induced electrical activity whilst that elicited by tolbutamide was relatively resistant to inhibition. 7. The nature and possible location of the glucoreceptor in pancreatic islet cells is discussed in relation to the origin and functional significance of glucose-induced electrical activity and insulin secretion.
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PMID:Pancreatic islet cells: effects of monosaccharides, glycolytic intermediates and metabolic inhibitors on membrane potential and electrical activity. 109 22

Fructose 2,6-bisphosphate (Fru-2,6-P2) is the most potent stimulator of 6-phosphofructo-1-kinase (PFK-1), a key enzyme of glycolysis. We studied whether this regulator is involved in the changes of glycolysis that can be induced experimentally in the isolated working rat heart. The glycolytic flux was assessed by the rate of detritiation of [2-3H]- and [3-3H]glucose, by lactate output and by the changes in glycogen content. A 20-40% increase in Fru-2,6-P2 content was observed when glycolysis was stimulated by increasing either the workload (by increasing both preload and afterload) or the concentration of glucose (from 2 to 11 mM), or by adding 7 microM insulin. Anoxia decreased the external work developed by the heart, stimulated glycolysis by activating glycogenolysis, but did not increase Fru-2,6-P2. The increase of Fru-2,6-P2 content observed after insulin, high workload or glucose load might be related to a stimulation of glucose transport, and/or an activation of 6-phosphofructo-2-kinase (PFK-2), the enzyme responsible for the synthesis of Fru-2,6-P2. Addition to the perfusate of 0.5 to 10 mM lactate, which is a preferred substrate for the heart, with pyruvate in a 10:1 ratio, induced a dose-dependent inhibition of the glycolytic flux through PFK-1, with a maximal inhibition of 75% at 5 mM lactate. The accumulation of hexose 6-phosphates without change in fructose 1,6-bisphosphate and triose-phosphates concentrations confirmed that the inhibition of glycolysis was mainly exerted on PFK-1. This inhibition resulted from a doubling of the citrate concentration, an inhibitor, and from 75% decrease in Fru-2,6-P2. Despite the inhibition of glycolysis, glucose phosphorylation was barely affected by lactate, suggesting a change in glucose metabolism. Indeed, lactate induced a dose-dependent increase in glycogen content, which doubled at 5 mM lactate, reaching the level obtained after addition of 7 microM insulin. Increased glycogen synthesis was explained by the accumulation of UDP glucose, the substrate, and glucose 6-phosphate, a stimulator of glycogen synthase. We conclude that, during aerobiosis, Fru-2,6-P2 can be regarded as a glycolytic signal which is switched on by glucose availability, workload and insulin, and which is switched off by the availability of alternative oxidative substrates such as lactate. The latter also controls glucose metabolism by diverting glucose from glycolysis to glycogen synthesis.
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PMID:Role of fructose 2,6-bisphosphate in the control of glycolysis. Stimulation of glycogen synthesis by lactate in the isolated working rat heart. 844 85