phosphocreatine and Hypoglycemia

Topics: Adenosine Triphosphate; Blood Glucose; Brain; C-Peptide; Energy Metabolism; Hormones; Humans; Hydrogen-Ion Concentration; Hypoglycemia; Insulin; Lactic Acid; Male; Phosphocreatine; Young Adult

Hypoglycemia is common during development and is associated with the risk of neurodevelopmental deficits in human infants. The effects of hypoglycemia on the developing hippocampus are poorly understood. The sequential changes in energy substrates, amino acids and phosphocreatine were measured from the hippocampus during 180 min of insulin-induced hypoglycemia (blood glucose < 2.5 mmol/L) in 14-day-old rats using in vivo(1)H NMR spectroscopy. Hypoglycemia resulted in neuroglycopenia (brain glucose < 0.5 micromol/g). However, the phosphocreatine/creatine (PCr/Cr) ratio was maintained in the physiological range until approximately 150 min of hypoglycemia, indicating that energy supply was sufficient to meet the energy demands. Lactate concentration decreased soon after the onset of neuroglycopenia. Beyond 60 min, glutamine and glutamate became the major energy substrates. A precipitous decrease in the PCr/Cr ratio, indicative of impending energy failure occurred only after significant depletion of these amino acids. Once glutamate and glutamine were significantly exhausted, aspartate became the final energy source. N-acetylaspartate concentration remained unaltered, suggesting preservation of neuronal/mitochondrial integrity during hypoglycemia. Correction of hypoglycemia normalized the PCr/Cr ratio and partially restored the amino acids to pre-hypoglycemia levels. Compensatory neurochemical changes maintain energy homeostasis during prolonged hypoglycemia in the developing hippocampus.

Topics: Animals; Animals, Newborn; Brain Chemistry; Chronic Disease; Energy Metabolism; Glucose; Glutamic Acid; Glutamine; Glycolysis; Hippocampus; Homeostasis; Humans; Hypoglycemia; Infant Nutrition Disorders; Infant, Newborn; Lactic Acid; Magnetic Resonance Spectroscopy; Neurons; Oxidative Phosphorylation; Phosphocreatine; Rats; Rats, Sprague-Dawley

This study aimed to examine brain energy metabolism during moderate insulin-induced hypoglycaemia in Type 1 diabetic patients and healthy volunteers.. Type 1 diabetic patients (mean diabetes duration 13 +/- 2.5 years; HbA1c 6.8 +/- 0.3%) and matched controls were studied before, during (0-120 min) and after (120-240 min) hypoglycaemic (approximately 3.0 mmol/l) hyperinsulinaemic (1.5 mU x kg(-1) min(-1)) clamp tests. Brain energy metabolism was assessed by in vivo 31P nuclear magnetic resonance spectroscopy of the occipital lobe (3 Tesla, 10-cm surface coil).. During hypoglycaemia, the diabetic patients showed blunted endocrine counter-regulation. Throughout the study, the phosphocreatine:gamma-ATP ratios were lower in the diabetic patients (baseline: controls 3.08 +/- 0.29 vs diabetic patients 2.65 +/- 0.43, p<0.01; hypoglycaemia: 2.97 +/- 0.38 vs 2.60 +/- 0.35, p<0.05; recovery: 3.01 +/- 0.28 vs 2.60 +/- 0.35, p<0.01). Intracellular pH increased in both groups, being higher in diabetic patients (7.096 +/- 0.010 vs. 7.107 +/- 0.015, p<0.04), whereas intracellular magnesium concentrations decreased in both groups (controls: 377 +/- 33 vs 321 +/- 39; diabetic patients: 388 +/- 47 vs 336 +/- 68 micromol/l; p<0.05).. Despite a lower cerebral phosphocreatine:gamma-ATP ratio in Type 1 diabetic patients at baseline, this ratio does not change in control or diabetic patients during modest hypoglycaemia. However, both groups exhibit subtle changes in intracellular pH and intracellular magnesium concentrations.

Topics: Adenosine Triphosphate; Adult; Blood Glucose; Brain Chemistry; Diabetes Mellitus, Type 1; Energy Metabolism; Glucose Clamp Technique; Hormones; Humans; Hypoglycemia; Magnetic Resonance Spectroscopy; Male; Phosphocreatine

Lipopolysaccharide (LPS) produces varied systemic metabolic effects. We studied the effects of LPS on the cardiac fatty acid profile and its relationship to energy metabolism and inflammatory mediators that included TNF-alpha and nitric oxide synthase (NOS) in 10-day-old neonatal rat pups. Rat pups received an i.p. injection of LPS after a 4-hour starvation period, followed by collection of blood and cardiac tissue 4 h following LPS administration. Compared to controls, LPS induced significant hypoglycemia and hyperlactacidemia, suggesting the development of endotoxic shock. The result was a significant depression in total fatty acid levels as well as non-esterified fatty acid in the cardiac tissue of the LPS-treated pups. In addition, LPS-treated pups also showed a significant increase in TNF-alpha, NOS levels with a depressed redox state and energy metabolism in cardiac tissue. These observations suggest that endotoxic shock in 10-day-old rat pups induces a systemic inflammatory response with a depression in fatty acid metabolism that may contribute to myocardial failure.

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Biomarkers; Blood Glucose; Energy Metabolism; Fatty Acids; Homeostasis; Hypoglycemia; Lactic Acid; Lipopolysaccharides; Myocardium; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Oxidative Stress; Phosphocreatine; Rats; Rats, Sprague-Dawley; Salmonella enteritidis; Tumor Necrosis Factor-alpha

The present study examined the effect of nefiracetam on ischemic brain damage by monitoring population spikes (PSs) in the dentate gyrus of guinea pig hippocampal slices; assaying high-energy phosphates (ATP and CrP) in guinea pig hippocampal slices; and monitoring whole-cell membrane-currents and intracellular Ca(2+) levels in cultured hippocampal neurons. Twenty-minute ischemic insult to slices, i.e., deprivation of glucose and oxygen from artificial cerebrospinal fluid, abolished PSs. As compared with only 35% recovery of the PS amplitude for control, PS amplitude reversed to 65% of basal levels 40 min after returning normal conditions by treatment with nefiracetam (0.01 microM). Ischemic insult reduced the levels of adenosine triphosphate (ATP) and creatine phosphate (CrP) in slices, and when returned to normal conditions, recovering to 70 and 85% of basal values, respectively, 30 min after returning normal conditions. Nefiracetam (0.01 microM) facilitated the recovery of ATP and CrP, reaching 110 and 140% of basal values, respectively. Nefiracetam inhibited N-methyl-D-aspartate (NMDA)-evoked currents to 35% of basal amplitudes. Likewise, nefiracetam (0.01 microM) inhibited intracellular Ca(2+) rise through NMDA receptor channels to 30% of basal levels. The results of the present study, thus, suggest that nefiracetam has the potential to protect against ischemic brain damage, possibly in part by preventing from accumulation of intracellular calcium through NMDA receptor channels.

Topics: Adenosine Diphosphate; Animals; Calcium; Cells, Cultured; Electrophysiology; Energy Metabolism; Glucose; Guinea Pigs; Hippocampus; Hypoglycemia; Hypoxia, Brain; In Vitro Techniques; Neuroprotective Agents; Patch-Clamp Techniques; Phosphocreatine; Pyrrolidinones; Receptors, N-Methyl-D-Aspartate; Synaptic Transmission

Using the blood-free perfused rat brain, we examined the redox behavior of cytochrome oxidase of two chromophores, heme a + a3 and copper. When perfusate inflow was stopped to induce global ischemia, the reduction of heme a + a3 was triphasic, with a rapid phase, a slow phase, and a second rapid phase. In contrast, the reduction of copper was monophasic after the rapid phase of heme a + a3. The triphasic reduction of heme a + a3 was diminished by energy-depleting treatments, such as addition of an uncoupler. The time course of the reduction of copper was not affected by the energy depletion. During global ischemia the decrease in creatine phosphate nearly paralleled the reduction of heme a + a3, whereas ATP remained at the control level until approximately 60% of heme a + a3 was reduced in the rapid phase. In the slow phase, ATP started to decrease with the reduction of copper. The redox behavior of copper was similar to the slow phase of the reduction of heme a + a3 because of the higher oxygen affinity of copper than of heme a + a3. Therefore, the rapid phase of the reduction of heme a + a3 can be used as an alarm before a decrease in ATP, whereas the reduction of copper indicates a decrease in ATP under severe hypoxia. Thus the copper signal in noninvasive near-infrared spectroscopy is a useful parameter for the clinical setting.

Topics: Animals; Brain; Carbonyl Cyanide m-Chlorophenyl Hydrazone; Copper; Electroencephalography; Electron Transport Complex IV; Energy Metabolism; Heme; Hypoglycemia; Hypoxia, Brain; Ischemic Attack, Transient; Male; Mitochondria; Oxidation-Reduction; Perfusion; Phosphocreatine; Rats; Rats, Wistar

The effect of insulin induced hypoglycemia on cerebral energy metabolism was examined in four newborn piglets. Cerebral energy metabolism was assessed using in vivo 31P-nuclear magnetic resonance spectroscopy. It was demonstrated that the normal level of phosphocreatine/inorganic phosphate (PCr/Pi), an indicator of phosphorylation potential, was maintained at a blood glucose level of 40 mg/dL or above, whereas when blood glucose was reduced to less than 40 mg/dL, PCr/Pi rapidly decreased in parallel with this. Below the critical blood glucose level of 40 mg/dL, a positive correlation (y = 0.02x + 0.632; r = 0.668; P < 0.001) existed between blood glucose and PCr/Pi. In the present investigation, a reduction of blood glucose level to 20 mg/dL or lower resulted in a PCr/Pi of less than 1, indicating a state of cerebral energy failure. The intracellular pH (pHi) was 7.08 +/- 0.05 at the onset and 7.15 +/- 0.07 in the hypoglycemic state, indicating no significant difference between the two groups. The present study has clarified that cerebral energy failure occurs when the blood glucose level is about 20 mg/dL or lower. The critical point of blood glucose exists to maintain brain energy metabolism.

Topics: Animals; Animals, Newborn; Brain; Disease Models, Animal; Energy Metabolism; Hypoglycemia; Insulin; Magnetic Resonance Spectroscopy; Phosphocreatine; Phosphorus Radioisotopes; Swine

Hippocampal slices were transiently exposed to an oxygen- and glucose-free environment which causes a pronounced drop of both ATP and creatine phosphate, an anoxic depolarization, and an incomplete recovery of synaptically evoked population spike in the CA1 region after 1 h (48.5 +/- 3.6% of baseline values). This recovery could be markedly enhanced by the application of N-methyl-D-aspartate receptor antagonists. To examine the influence of metabotropic glutamate receptors on neuronal recovery from hypoxia/hypoglycemia, we applied various antagonists and agonists of the metabotropic glutamate receptors to the bath during the interval from 20 min before to 10 after hypoxia/hypoglycemia. The metabotropic glutamate receptor antagonists (+)-alpha-methyl-4-carboxyphenylglycine and L-2-3- amino-phosphonopropionic acid were both able to enhance the population spike recovery significantly. However, the mixed metabotropic glutamate receptor agonist 1S,3R-1-aminocyclopentane-1,3-dicarboxylic acid also exhibited a protective effect on population spike recovery, leaving the anoxic depolarization and N-methyl-D-aspartate responses during the hypoxia/hypoglycemia untouched. With the help of more subtype-specific agonists, we found that an activation of phospholipase C coupled (class 1) metabotropic glutamate receptors prior to hypoxia/hypoglycemia may be responsible for the protective effect seen with 1S, 3R-1-aminocyclopentane-1,3-dicarboxylic acid, because the specific class 1 metabotropic glutamate receptor agonist trans-azetidine-2,4-dicarboxylic acid appeared to be highly protective, but only if it was applied 20 min before the hypoxia/hypoglycemia. An activation of class 2 metabotropic glutamate receptors by (2S,1'R,2'R,3'R)-2-(2,3-dicarboxycyclopropyl)glycine, which inhibits adenylyl cyclase activity, led to a marked deterioration of the population spike recovery and even to a total prevention of the protective effect of the N-methyl-D-aspartate agonist D-2-amino-5-phosphonopentanoic acid. Our data suggest that prior activation of class 1 metabotropic glutamate receptors is beneficial, while their activation during hypoxia/hypoglycemia is detrimental. Furthermore, the activation of class 2 metabotropic glutamate receptors decreases the recovery from hypoxia/hypoglycemia.

Topics: Adenosine Triphosphate; Animals; Cycloleucine; Electrophysiology; Energy Metabolism; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Hippocampus; Hypoglycemia; Hypoxia, Brain; In Vitro Techniques; Male; N-Methylaspartate; Neurons; Phosphocreatine; Pyramidal Cells; Rats; Rats, Wistar; Receptors, Metabotropic Glutamate

(1) The energy state and free intracellular calcium concentration ([Ca2+]i) of superfused cortical slices were measured in moderate hypoxia (approximately 65 microM O2), in mild hypoglycaemia (0.5 mM glucose), and in combinations of the two insults using 19F and 31P NMR spectroscopy. (2) Neither hypoxia nor hypoglycaemia alone caused any significant change in [Ca2+]i. Hypoxia caused a 40% fall in phosphocreatine (PCr) content but not in ATP level, and hypoglycaemia produced a slight fall in both (as expected from previous studies). These changes in the energy state recovered on return to control conditions. (3) A combined sequential insult (hypoxia, followed by hypoxia plus hypoglycaemia) produced a 100% increase in [Ca2+]i and a decrease in PCr level to approximately 25% of control. The reverse combined sequential insult (hypoglycaemia, followed by hypoglycaemia plus hypoxia) had the same effect. On return to control conditions there was some decrease in [Ca2+]i and a small increase in PCr content, but neither recovered to control levels. (4) Exposure of the tissue to the combined simultaneous insult (hypoxia plus hypoglycaemia) immediately after the control spectra had been recorded resulted in a fivefold increase in [Ca2+]i and a similar decrease in PCr level to 20-25% of control. There was little if any change of [Ca2+]i or PCr level on return to control conditions. (5) These results are discussed in terms of metabolic adaptation of some but not all of the cortical cells to the single type of insult, which renders the tissues less vulnerable to the combined insult.

Topics: Adenosine Triphosphate; Animals; Calcium; Cerebral Cortex; Fluorine; Guinea Pigs; Hypoglycemia; Hypoxia; In Vitro Techniques; Kinetics; Magnetic Resonance Spectroscopy; Phosphocreatine; Phosphorus

The effect of severe insulin-induced hypoglycemia on the activity of the pyruvate dehydrogenase enzyme complex (PDHC) was investigated in homogenates of frozen rat cerebral cortex during burst suppression EEG, after 10, 30, and 60 min of isoelectric EEG, and after 30 and 180 min and 24 h of recovery following 30 min of hypoglycemic coma. Changes in PDHC activity were correlated to levels of labile organic phosphates and glycolytic metabolites. In cortex from control animals, the rate of [1-14C]pyruvate decarboxylation was 7.1 +/- 1.3 U/mg of protein, or 35% of the total PDHC activity. The activity was unchanged during burst suppression EEG whereas the active fraction increased to 81-87% during hypoglycemic coma. Thirty minutes after glucose-induced recovery, the PDHC activity had decreased by 33% compared to control levels, and remained significantly depressed after 3 h of recovery. This decrease in activity was not due to a decrease in the total PDHC activity. At 24 h of recovery, PDHC activity had returned to control levels. We conclude that the activation of PDHC during hypoglycemic coma is probably the result of an increased PDH phosphatase activity following depolarization and calcium influx, and allosteric inhibition of PDH kinase due to increased ADP/ATP ratio. The depression of PDHC activity following hypoglycemic coma is probably due to an increased phosphorylation of the enzyme, as a consequence of an imbalance between PDH phosphatase and kinase activities. Since some reduction of the ATP/ADP ratio persisted and since the lactate/pyruvate ratio had normalized by 3 h of recovery, the depression of PDHC most likely reflects a decrease in PDH phosphatase activity, probably due to a decrease in intramitochondrial Ca2+.

Topics: Adenosine Triphosphate; Animals; Cerebral Cortex; Electroencephalography; Energy Metabolism; Glucose; Glycogen; Glycolysis; Hypoglycemia; Insulin; Male; Phosphocreatine; Pyruvate Dehydrogenase Complex; Rats; Rats, Inbred Strains

Chemically induced hypoglycemia and anoxia were evaluated in embryonic day 13 chicken retina to determine if excitotoxicity was a consequence of these conditions and if this was preceded by the net release of glutamate or aspartate. Retina incubated with iodoacetate (IOA), to inhibit glycolysis, or potassium cyanide (KCN), to inhibit electron transport, produced histological lesions similar to those found with N-methyl-D-aspartate (NMDA) or kainate. An increase in gamma-aminobutyric acid release, which has been used previously as a marker of excitatory amino acid-induced acute excitotoxicity, was also found to occur with IOA or KCN treatment. The NMDA antagonists 2-amino-5-phosphonovalerate and MK-801 [(+)-11-dihydro-5H-dibenzo[a,d]cyclohepten,5,10-imine maleate] protected retina from IOA- or KCN-induced lesioning and prevented the increase in gamma-aminobutyric acid release. The non-NMDA glutamate antagonist, 6-nitro,7-cyano-quinoxaline,2,3-dion, had little effect suggesting that the damage was mediated predominantly by the NMDA receptor. Extracellular glutamate and aspartate concentrations remained low (less than 0.2 microM) throughout incubation. Thus, the data furnish no evidence that an increase in released glutamate or aspartate is responsible for the activation of the NMDA receptor. Lactate production, ATP and phosphocreatine concentrations were also measured. ATP and phosphocreatine, but not lactate, levels were correlated with the induction of an acute excitotoxic lesion. The depletion of high energy phosphates and the first appearance of acute excitotoxicity were temporally distinct. Possible mechanisms linking metabolic inhibition and NMDA receptor-mediated acute excitotoxicity are discussed.

Topics: Adenosine Triphosphate; Amino Acids; Animals; Aspartic Acid; Chick Embryo; Electron Transport; Glycolysis; Hypoglycemia; Hypoxia; Iodoacetates; Iodoacetic Acid; N-Methylaspartate; Phosphocreatine; Receptors, Glutamate; Receptors, Neurotransmitter; Retina

Whether severe hypoglycemia alone or in combination with hyperketonemia might cause deterioration of cardiac function has been controversial. Therefore, the influence of acute hypoglycemia (mean 33 mg/dL) with and without hyperketonemia (mean 1.3 and 3.3 mM) on cardiac function, substrate utilization, and myocardial high energy phosphate levels was studied in 10 mongrel dogs. After 45 min of hypoglycemia, mean aortic pressure, total peripheral resistance, and myocardial oxygen consumption had increased significantly, but other hemodynamic parameters and regional myocardial function had not changed. Additional infusion of 3-hydroxybutyrate did not affect hemodynamic variables significantly. During both metabolic interventions in vivo phosphorus-31 nuclear magnetic resonance spectroscopy showed stable levels of myocardial phosphocreatinine, ATP, as well as the phosphocreatinine/ATP (3.0-3.2) ratio. Biochemical measurements revealed that hyperketonemia led to significant alterations in arterial concentrations and arteriocoronary venous differences of selected citric acid cycle intermediates, thus confirming previous reports which suggested a blockade of the 2-oxoglutarate-dehydrogenase reaction induced by ketone body oxidation. However, despite this blockade, the energy supply to the heart was not impaired as shown by normal nuclear magnetic resonance spectroscopy and cardiac performance. It is speculated, that the blockade might be due to an enhanced NADH/NAD ratio.

Topics: Adenosine Triphosphate; Animals; Citric Acid Cycle; Dogs; Energy Metabolism; Heart; Hemodynamics; Hypoglycemia; Ketone Bodies; Magnetic Resonance Spectroscopy; Myocardium; Phosphocreatine

Hypoglycaemia and anoxia both cause massive release of glutamate from the brain in vivo, and the nature of this release was investigated using guinea-pig cerebral-cortical synaptosomes and iodoacetate and rotenone to simulate the energetic consequences of these conditions. Glutamate release (by continuous fluorimetry), cytoplasmic free Ca2+ (by fura-2), membrane potentials, ATP, ADP and creatine phosphate were determined in parallel, following the addition of iodoacetate or rotenone, alone or in combination. Ca2+-dependent glutamate release had a high energy requirement which could only be satisfied by aerobic glycolysis. Respiration using endogenous substrates, or anaerobic glycolysis following rotenone, caused a progressive inhibition of Ca2+-dependent release, correlating with a decline in the total ATP/ADP ratio and creatine phosphate. With rotenone, an increase in Ca2+-independent glutamate release was observed, correlating with a decline in plasma membrane potential. Only a slight increase in free Ca2+ was seen. Rotenone plus iodoacetate caused an almost immediate collapse of ATP/ADP ratio and a parallel loss of Ca2+-dependent glutamate release before free Ca2+ had risen to a level sufficient for exocytosis. In contrast, Ca2+-independent glutamate release increased. The Ca2+-dependent release of L-glutamate had the characteristics of an exocytotic transmitter release mechanism, being energy-dependent and triggered by elevated cytoplasmic free Ca2+ concentration. A distinct Ca2+-independent release of cytoplasmic glutamate occurred by reversal of the Na+-coupled uptake carrier, which was accelerated by a decline in the Na+ gradient. It is concluded that the Ca2+-independent release of cytoplasmic glutamate may make the major contribution to the excitotoxic release of glutamate in hypoglycaemic and anoxic conditions.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Calcium; Cytosol; Energy Metabolism; Glutamates; Glutamic Acid; Guinea Pigs; Hypoglycemia; Membrane Potentials; Oxygen Consumption; Phosphocreatine; Rotenone; Synaptosomes

31P nuclear magnetic resonance (NMR) spectroscopy allows noninvasive studies of cerebral energy-rich phosphorous compounds in humans. In an attempt to characterize the relationship between peripheral blood glucose concentrations and whole-brain phosphate metabolism during insulin-induced hypoglycemia, 31P NMR spectra were obtained before and after intravenous injection of insulin (0.15 IU/kg body wt) in six men. Compared with prehypoglycemic measurements, no significant changes were found in brain content of Pi, sugar phosphates, phosphocreatine, phosphodiesters, and ATP, and brain pH remained constant during the experiment. These results show that the integrated brain profile of energy-rich phosphorous compounds is unaffected by experimental insulin-induced hypoglycemia in humans.

Topics: Adenosine Triphosphate; Adult; Brain; Energy Metabolism; Humans; Hydrogen-Ion Concentration; Hypoglycemia; Insulin; Magnetic Resonance Spectroscopy; Male; Organophosphates; Phosphates; Phosphocreatine; Sugar Phosphates

The effects of hypoxia and hypoglycaemia on the redox state in vitro have been studied. NADH and NAD+ were extracted simultaneously from superfused cerebral cortex slices and assayed by bioluminescence. The results show a nonsignificant increase in NADH and the redox ratio in "mild hypoxia," whereas "severe hypoxia" produced an increase of over 200% in NADH and in the NADH/NAD+ ratio. When the glucose in the incubation medium was reduced from its control value of 10 mM to 0.5 mM, significant decreases in NADH and the redox ratio to 60% of control value were observed. Further decreasing the glucose to 0.2 mM gave lower levels of NADH and the redox ratio (40% of control). The effects on the redox state of alternative substrates to glucose were also tested. Replacement of glucose by 10 mM pyruvate decreased the NADH by 77% and the NADH/NAD+ ratio by 79%. Replacement of glucose with 10 mM lactate gave decreases of 70% and 71%, respectively, whereas in the presence of 15 mM 2-deoxyglucose and 5 mM glucose, the NADH was decreased by 56% and the ratio by 50%. The results are discussed in relation to levels of creatine phosphate and ATP, as well as evoked action potentials, observed from parallel studies.

Topics: Adenosine Triphosphate; Animals; Brain; Female; Glucose; Guinea Pigs; Hypoglycemia; Hypoxia, Brain; In Vitro Techniques; Lactates; Lactic Acid; NAD; Oxidation-Reduction; Oxygen; Phosphocreatine; Pyruvates; Pyruvic Acid

Severe acute hypoglycaemia with isoelectric electroencephalogram induces a major deterioration of the energy state and amino acid contents of the brain. During post-hypoglycaemia recovery of adult animals, brain glucose concentrations return to normal values, whereas glycogen turnover remains low as aspartate and pyruvate concentrations increase. ATP levels rise, but the adenine-nucleotide pool remains small despite return to normal of ADP and AMP. Brain phosphocreatine levels return to normal values, with reciprocal changes in creatine content. In adult rats one also notes during recovery an increase in brain glutamine and glutamate, whereas the gamma-aminobutyrate returns to normal. Finally, ammonium and aspartate remain below, and alanine remains above normal values. Aging has no effect on cerebral metabolic disturbances induced by hypoglycaemia, but it influences the cerebral metabolic restoration processes that develop during post-hypoglycaemia recovery. The restitution of cerebral metabolites is weaker in mature and senescent rats than in adult rats. In the oldest rats, in particular, the concentrations of most of the amino acids and of adenyl nucleotides remain largely abnormal. The effects of dihydroergocristine, erbunamonine, raubasine, almitrine and of the almitrine-raubasine combination on post-hypoglycaemia recovery were evaluated in adult, mature and senescent rats. During recovery these pharmacological agents exert different effects on glycolytic metabolites, amino acids and energy-rich phosphates.

Topics: Adenosine Triphosphate; Aging; Almitrine; Animals; Anti-Inflammatory Agents, Non-Steroidal; Brain; Central Nervous System Stimulants; Glucose; Hypoglycemia; Male; Phosphocreatine; Piperazines; Rats; Rats, Inbred Strains; Secologanin Tryptamine Alkaloids; Sodium Chloride; Time Factors; Yohimbine

Metabolic alterations in amino acids, high-energy phosphates, and intracellular pH during and after insulin hypoglycemia in the rat brain was studied in vivo by 1H and 31P nuclear magnetic resonance (NMR) spectroscopy. Sequential accumulations of 1H and 31P spectra were obtained from a double-tuned surface coil positioned over the exposed skull of a rat while the electroencephalogram was recorded continuously. The transition to EEG silence was accompanied by rapid declines in phosphocreatine, nucleoside triphosphate, and an increase in inorganic orthophosphate in 31P spectra. In 1H spectra acquired during the same time interval, the resonances of glutamate and glutamine decreased in intensity while a progressive increase in aspartate was observed. Following glucose administration, glutamate and aspartate returned to control levels (recovery half-time, 8 min); recovery of glutamine was incomplete. An increase in lactate was detected in the 1H spectrum during recovery but it was not associated with any change in the intracellular pH as assessed in the corresponding 31P spectrum. Phosphocreatine returned to control levels following glucose administration, in contrast to nucleoside triphosphate and inorganic orthophosphate which recovered to only 80% and 200% of their control levels, respectively. These results show that the changes in cerebral amino acids and high-energy phosphates detected by alternating the collection of 1H and 31P spectra allow for a detailed assessment of the metabolic response of the hypoglycemic brain in vivo.

Topics: Amino Acids; Animals; Aspartic Acid; Brain; Electroencephalography; Glutamates; Glutamic Acid; Glutamine; Hydrogen-Ion Concentration; Hypoglycemia; Insulin; Lactates; Lactic Acid; Magnetic Resonance Spectroscopy; Nucleotides; Phosphates; Phosphocreatine; Rats

Severe hypoglycemia, causing the cessation of spontaneous EEG, induced in cerebral cortex of rats of different ages, causes gross energy failure and extensive derangement of both carbohydrate and amino acid contents. During posthypoglycemic recovery of adult rats, there was moderate restitution of energy metabolism and both ATP concentration and adenine nucleotide pool remained still reduced, even if the creatine phosphate and ADP contents were close to normal. During recovery of adult rats there was a rise in glutamate and glutamine concentrations and the perturbated aspartate and gamma-aminobutyrate cerebral contents normalized. Ammonia content decreased to normal, while alanine content was markedly elevated. Aging does not affect the cerebral metabolic derangements occurring in severe hypoglycemia, but rather the metabolic changes that the brain tend to reverse during the posthypoglycemic restitution. In fact, there was lower restitution of the contents of cerebral cortical metabolites of "mature" and "senescent" rats in comparison with "adult" ones. Particularly, in older brains the contents of many amino acids and adenylate nucleotides remained largely abnormal.

Topics: Adenine Nucleotides; Aging; Animals; Cerebral Cortex; Citric Acid Cycle; Electroencephalography; Energy Metabolism; Glycolysis; Hypoglycemia; Male; Phosphocreatine; Rats

In the cerebral cortices of rats, during insulin-induced hypoglycemia, changes in the concentrations of labile phosphate compounds [ATP, ADP, AMP, and phosphocreatine (PCr)] and glycolytic metabolites (lactate, pyruvate, and glucose) as well as phospholipids and free fatty acids (FFAs) were studied in relation to extracellular potassium and calcium activities. Changes in extracellular calcium and potassium activities occurred at approximately the onset of isoelectricity . The extracellular calcium activity dropped from 1.17 +/- 0.14 mM to 0.18 +/- 0.28 mM and the potassium activity rose from 3.4 +/- 0.94 mM to 48 +/- 12 mM (means +/- SD). Minutes prior to this ionic change the levels of ATP, PCr, and phospholipids were unchanged while the levels of FFAs remained unchanged or slightly elevated. Following the first ionic change the steady-state levels of ATP decreased by 40%, from 2.42 to 1.56 mumol/g. PCr levels decreased by 75%, from 4.58 to 1.26 mumol/g. Simultaneously, the levels of FFAs increased from 338 to 642 nmol/g, arachidonic acid displaying the largest relative increase, 33 to 130 nmol/g. The first ionic change was followed by a short period of normalization of ionic concentrations followed by a sustained ionic change. This was accompanied by a small additional decrease in ATP (to 1.26 mumol/g). The FFA levels increased to 704 nmol/g. There was a highly significant negative correlation between the levels of FFAs and the energy charge of the tissue. The formation of FFAs was accompanied by a decrease in the phospholipid pool. The largest relative decrease was observed in the inositol phosphoglycerides, followed by serine and ethanolamine phosphoglycerides.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adenosine Triphosphate; Animals; Brain; Calcium; Energy Metabolism; Extracellular Space; Fatty Acids, Nonesterified; Hypoglycemia; Phosphocreatine; Phospholipids; Potassium; Rats; Time Factors

A system has been developed for performing 31P-n.m.r. studies on cerebral tissues superfused in vitro, and gives results comparable with those reported from studies in vivo. Under optimal superfusion conditions [10 mM-glucose and O2/CO2 (19:1)] the tissue concentrations of phosphocreatine and ATP were calculated to be approx. 3.1 and 1.3 mumol/g respectively. When the glucose of the superfusing medium was lowered to 0.5 mM, slightly decreased sugar phosphate peaks were observed, but there was no detectable change in [ATP] or [phosphocreatine]. At 0.2 mM-glucose, significantly decreased concentrations of phosphocreatine and ATP were observed. Substitution of pyruvate plus malate for glucose did not decrease levels of phosphocreatine and ATP. When the superfusing medium was gassed with air/CO2 (19:1; 'mild hypoxia'), there was an appreciable fall in sugar phosphates and phosphocreatine with no detectable effect on ATP. In the presence of N2/CO2 (19:1; 'severe hypoxia', since O2 was not completely excluded), concentrations of phosphocreatine fell considerably, but with little effect on ATP. The results demonstrate the feasibility of studying cerebral energy metabolism in vitro using the non-invasive 31P-n.m.r. technique and are discussed in relation to the sensitivity of cerebral tissues to metabolic insults in vitro and in vivo.

Topics: Animals; Brain; Energy Metabolism; Glucose; Guinea Pigs; Hypoglycemia; In Vitro Techniques; Magnetic Resonance Spectroscopy; Malates; Male; Oxygen; Phosphocreatine; Pyruvates; Pyruvic Acid; Sugar Phosphates

Topics: Adenosine Triphosphate; Ammonia; Animals; Behavior, Animal; Blood Glucose; Brain; Cerebrovascular Circulation; Female; Hypoglycemia; Oxygen Consumption; Phosphocreatine; Rats; Regional Blood Flow

Regional CNS levels of glucose reserves, glycolytic intermediates, and high-energy phosphate reserves were measured in insulin-treated, hypoglycemic rats and correlated with EEG activity. Intravenous administration of insulin to paralyzed, ventilated animals causes concomitant reduction of blood glucose levels and progressive abnormality and eventual loss of EEG activity. In all regions of brain examined, glucose and glycogen levels decrease until they are essentially depleted, and glucose-6-phosphate and fructose-1,6-biphosphate fall approximately 80%. Pyruvate levels decrease 50% in cerebral cortex and brain stem and a lesser amount in striatum, hippocampus, thalamus, and cerebellum. Lactate levels fall 50-60% in all regions except cerebellum, where no change is observed. ATP and phosphocreatine levels remain normal until the EEG is isoelectric, and then decrease in all regions except cerebellum. These results demonstrate that hypoglycemia does not have a uniform effect on brain glucose and energy metabolism, and cerebellum seems to be relatively protected.

Topics: Adenosine Triphosphate; Animals; Brain; Electroencephalography; Fructosediphosphates; Glucose; Glucose-6-Phosphate; Glucosephosphates; Glycogen; Hypoglycemia; Insulin; Lactates; Lactic Acid; Phosphocreatine; Pyruvates; Pyruvic Acid; Rats

Swiss-Albino female mice weighing 20 g were rendered hypoglycemic by injecting insulin (2 units/kg). Animals were sacrificed at 40 min (pre-coma), 2 h (coma) and 4.5 h (recovery) after insulin injection by rapid submersion in liquid N2. Following sectioning at 20 micrometer, samples from the ascending reticular activating system and the inferior colliculus were freeze-dried and assayed for glucose, lactate, ATP and phosphocreatine (PCr). There was a preferential effect of hypoglycemia on ATP and PCr in cells of the ascending reticular activating system. ATP was depleted 30%, and PCr 55% in the pre-coma stage. ATP and PCr in cells from the inferior colliculus were not decreased. This selective effect on cells of the ascending reticular activating system followed by coma suggests that the coma per se may not represent total failure of the organism, but rather a compensatory mechanism designed to permit the animal to correct its compromised energy status.

Topics: Adenosine Triphosphate; Animals; Brain; Energy Metabolism; Female; Glucose; Hypoglycemia; Insulin; Insulin Coma; Kinetics; Lactates; Mice; Organ Specificity; Phosphocreatine

Previous results have shown that severe, prolonged hypoglycemia leads to neuronal cell damage in, among other structures, the cerebral cortex and the hippocampus but not the cerebellum. In order to study whether or not this sparing of cerebellar cells is due to preservation of cerebellar energy stores, hypoglycemia of sufficient severity to abolish spontaneous EEG activity was induced for 30 and 60 min. At the end of these periods of hypoglycemia, as well as after a 30 min recovery period, cerebellar tissue was sampled for biochemical analyses or for histopathological analyses or for histopathological analyses by means of light and electron microscopy. After 30 min of hypoglycemia. the cerebellar energy state, defined in terms of the phosphocreatine, ATP, ADP, and AMP concentrations, was better preserved than in the cerebral cortex. After 60 min, gross deterioration of cerebellar energy state was observed in the majority of animals, and analyses of carbohydrate metabolites and amino acids demonstrated extensive consumption of endogenous substrates. In spite of this metabolic disturbance, histopathologic alterations were surprisingly discrete. After 30 min, no clear structural changes were observed. After 60 min, only small neurons in the molecular layer (basket cells) were affected, while Purkinje cells and granule cells showed few signs of damage. The results support our previous conclusion that the pathogenesis of cell damage in hypoglycemia is different from that in hypoxia-ischemia and indicate that other mechanisms than energy failure must contribute to neuronal cell damage in the brain.

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Cerebellum; Cerebral Cortex; Creatine; Glucose; Hypoglycemia; Insulin; Male; Neurons; Phosphocreatine; Purkinje Cells; Rats; Rats, Inbred Strains

The effects of insulin-induced hypoglycemic stupor and subsequent treatment with glucose on mouse cerebral cortical, cerebellar and brain stem levels of glucose, glycogen, ATP, phosphocreatine, glutamate, aspartate and GABA and on cerebral cortical and cerebellar levels of cyclic AMP and cyclic GMP have been measured. Hypoglycemia decreased glucose, glycogen and glutamate levels and had no effect on ATP levels in all three regions of brain. GABA levels were decreased only in cerebellum. Aspartate levels rose in cerebral cortex and brain stem, and creatine phosphate increased in cerebral cortex and cerebellum. In the hypoglycemic stuporous animals, cyclic GMP levels were elevated in cerebral cortex and depressed in cerebellum whereas cyclic AMP levels were unchanged from control values. Intravenous administration of 2.5-3.5 mmol/kg of glucose to the hypoglycemic stuporous animals produced recovery of near normal neurological function within 45 s. Only brain glucose and aspartate levels returned to normal prior to behavioral recovery. These results suggest that of the several substances examined in this study, only glucose and perhaps aspartate have important roles in the biochemical mechanisms producing neurological abnormalities in hypoglycemic animals.

Topics: Adenosine Monophosphate; Adenosine Triphosphate; Amino Acids; Animals; Aspartic Acid; Behavior, Animal; Central Nervous System; Coma; Cyclic AMP; Cyclic GMP; gamma-Aminobutyric Acid; Glucose; Glutamic Acid; Glycogen; Hypoglycemia; Insulin; Male; Mice; Phosphocreatine; Recovery of Function

Topics: Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Blood Glucose; Carbon Dioxide; Cerebral Cortex; Creatine; Electroencephalography; Fasting; Hydrogen-Ion Concentration; Hypoglycemia; Insulin; Male; Oxygen; Phosphocreatine; Rats; Seizures; Time Factors

Topics: Acidosis; Adenosine Diphosphate; Adenosine Monophosphate; Adenosine Triphosphate; Animals; Blood Glucose; Blood Pressure; Body Temperature; Brain; Creatine; Energy Metabolism; Glucosephosphates; Glycogen; Hydrogen-Ion Concentration; Hyperglycemia; Hypoglycemia; Ischemia; Lactates; Phosphocreatine; Pyruvates; Rats

Topics: Adenosine Triphosphate; Animals; Brain; Brain Diseases; Brain Stem; Cerebellum; Cerebral Cortex; Corpus Striatum; Electroencephalography; Female; Glucose; Hippocampus; Hypoglycemia; Hypothalamus; Hypoxia, Brain; Insulin; Male; Mice; Oxygen Consumption; Phosphocreatine; Spinal Cord; Thalamus

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Blood Glucose; Blood-Brain Barrier; Brain; Brain Chemistry; Glucose; Glycogen; Glycolysis; Hypoglycemia; Hypoxia; Lactates; Liver; Mice; Phosphocreatine; Time Factors

Topics: Adenosine Triphosphate; Animals; Animals, Newborn; Brain; Brain Damage, Chronic; Cerebrosides; Cholesterol; DNA; Gangliosides; Glucose; Glycogen; Humans; Hypoglycemia; Infant, Newborn; Infant, Newborn, Diseases; Lipid Metabolism; Nerve Tissue Proteins; Organ Size; Phosphocreatine; Phospholipids; Rats; Sulfoglycosphingolipids

Topics: Adenosine Triphosphate; Anaerobiosis; Animals; Blood Glucose; Blood-Brain Barrier; Brain; Fluorometry; Fructose; Glucose; Glycogen; Hexokinase; Hypoglycemia; Hypoxia; Insulin; Ischemia; Kinetics; Mice; Permeability; Phosphocreatine

Topics: Adenine Nucleotides; Animals; Blood Glucose; Brain; Cerebral Cortex; Electroencephalography; Glycogen; Glycolysis; Hypoglycemia; Insulin; Lactates; Phosphates; Phosphocreatine; Pyruvates; Rabbits