glycogen and Hypercapnia

Recent in vitro data suggest that astrocytes may modulate respiration. To examine this question in vivo, we treated 5-day-old rat pups with methionine sulfoximine (MS), a compound that alters carbohydrate and glutamate metabolism in astrocytes, but not neurons. MS-treated pups displayed a reduced breathing frequency (f) in baseline conditions relative to saline-treated pups. Hypercapnia (5% CO(2)) increased f in both groups, but f still remained significantly lower in the MS-treated group. No differences between treatment groups in the responses to hypoxia (8% O(2)) were observed. Also, MS-treated rats showed an enhanced accumulation of glycogen in neurons of the facial nucleus, the nucleus ambiguus, and the hypoglossal nucleus, structures that regulate respiratory activity and airway patency. An altered transfer of nutrient molecules from astrocytes to neurons may underlie these effects of MS, although direct effects of MS upon neurons or upon peripheral structures that regulate respiration cannot be completely ruled out as an explanation.

Topics: Animals; Animals, Newborn; Astrocytes; Brain; Glycogen; Hypercapnia; In Situ Hybridization; Methionine Sulfoximine; Neurons; Rats; Receptors, Neurokinin-1; Respiration; Respiratory Function Tests; RNA, Messenger

Previously we have shown that hypercarbia produces a larger decrease in agonal glycolytic rate in 1-month-old swine than in newborns. In an effort to understand the mechanism responsible for this difference, we tested the hypothesis that hypercarbia produces age-related changes in the concentration of one or more effectors of phosphofructokinase activity. Specifically, in vivo 31P and 1H NMR spectroscopy was used to compare changes in lactate levels, intracellular pH, free magnesium concentration, and content of phosphorylated metabolites for these two age groups at three intervals during the first 1.5 min of complete ischemia in the presence or absence of hypercarbia (PaCO2 = 102-106 mm Hg). Hypercarbia produced the same drop in intracellular brain pH for both age groups, but the decrease in phosphocreatine level and increase in inorganic phosphate content were greater in 1-month-olds compared with newborns. During ischemia there was no difference between the magnitude of change in intracellular pH and levels of phosphocreatine and inorganic phosphate in hypercarbic 1-month-olds versus newborns. Under control conditions, i.e., normocarbia and normoxia, the free Mg2+ concentration was lower and the fraction of magnesium-free ATP was higher for newborns than 1-month-olds. However, there was no change in these variables for either age group during hypercarbia and early during ischemia. Thus, age-related differences in the relative decrease in agonal glycolytic rate during hypercarbia could not be explained by differences in intracellular pH, inorganic phosphate content, or free magnesium concentration. The [ADP]free at control was higher in newborns compared with 1-month-olds, and there was no age-related difference in [AMP]free. These variables did not change for newborns when exposed to hypercarbia, but for 1-month-olds [ADP]free and [AMP]free increased during hypercarbia relative to control values. High-energy phosphate utilization during ischemia for hypercarbic 1-month-olds was reduced by 74% compared with normocarbic 1-month-olds during ischemia, whereas the reduction in energy utilization (14%) was not significant for hypercarbic versus normocarbic newborns during ischemia.(ABSTRACT TRUNCATED AT 400 WORDS)

Topics: Acidosis; Animals; Animals, Newborn; Brain; Brain Chemistry; Death; Glycogen; Hydrogen; Hydrogen-Ion Concentration; Hypercapnia; Ischemia; Lactates; Magnesium; Magnetic Resonance Spectroscopy; Phosphorus; Swine; Swine, Miniature

The content of the free fatty acids, ketone bodies, total glycogen, glucose, adrenaline and noradrenaline and morpho-histochemical picture of the tissues of neuro-endocrinal system (hypophysis and adrenal) in the brain, heart, liver, skeletal muscles and blood of the white non-linear rats, were studied 2-3 min adaptation to complex atmosphere changes: gradual increase of the CO2, decrease of the O2, and cooling (in the condition of deep hypothermia the rectal temperature was--RT--19.1 +/- 0.1 degrees C). The same parameters were studied in 48 hrs after the same training (at normothermia) and in 2-3 min. after the same repeated training in 48 hrs after the first one, at RT--20.2 +/- 0.1 degrees C. The fluctuating character of the metabolism and of the regulating systems was shown.

Topics: Acetoacetates; Acetylcholinesterase; Adrenocorticotropic Hormone; Animals; Brain; Carbohydrate Metabolism; Epinephrine; Fatty Acids, Nonesterified; Glucose; Glycogen; Hypercapnia; Hypothalamo-Hypophyseal System; Hypothermia, Induced; Hypoxia; Lipid Metabolism; Liver; Male; Monoamine Oxidase; Muscles; Myocardium; Norepinephrine; Rats

Topics: Acute Disease; Alanine; Amino Acids; Ammonia; Anesthesia, General; Animals; Asparagine; Aspartic Acid; Carbohydrate Metabolism; Cerebral Cortex; Citric Acid Cycle; Fructosephosphates; gamma-Aminobutyric Acid; Glucosephosphates; Glutamates; Glutamine; Glycogen; Glycolysis; Hypercapnia; Lactates; Male; Pyruvates; Rats

Topics: Adenine Nucleotides; Amino Acids; Animals; Blood Pressure; Body Temperature; Brain; Carbohydrate Metabolism; Carbon Dioxide; Citrates; Citric Acid Cycle; Fructosephosphates; Glycerophosphates; Glycogen; Hydrogen-Ion Concentration; Hypercapnia; Male; NAD; Organophosphorus Compounds; Oxidation-Reduction; Oxygen; Pyruvates; Rats; Time Factors

Topics: Acute Disease; Adenosine Triphosphate; Alkaloids; Animals; Arrhythmias, Cardiac; Asphyxia; Drug Synergism; Electrocardiography; Epinephrine; Fluorides; Glycogen; Hypercapnia; Male; Norepinephrine; Quinidine; Rats; Vasopressins

Topics: Animals; Asphyxia; Fishes; Fresh Water; Glycogen; Hypercapnia; Hypoxia; Myocardium