glutaminase and Acute-Disease

In chronic metabolic acidosis in the rat, there is increased ammoniagenesis, gluconeogenesis and renal extraction of glutamine with induction of renal phosphate-dependent glutaminase (PDG). Because the stimulus for these changes is not yet clear and also because acute acidosis is the more common clinical problem, the present study deals mainly with the metabolism of glutamine in acute metabolic acidosis. When acute metabolic acidosis is produced in rats by administration of mineral acid or by causing them to swim, thus inducing a severe lactic acidosis, a factor is found in the plasma which stimulates renal glutamine uptake and ammoniagenesis in vivo as well as in vitro. Acute acidosis does not induce synthesis of PDG in the kidney but causes a change in enzyme kinetics. The plasma factor not only enhances glutamine entry into cells, but apparently causes a conformational change in PDG, as shown by an increase in V1.0mM/Vmax. Intestinal metabolism of glutamine is also stimulated in vivo and in vitro by the plasma factor of acute acidosis.

Topics: Acidosis; Acute Disease; Ammonia; Animals; Chronic Disease; gamma-Glutamyltransferase; Glutamate Dehydrogenase; Glutaminase; Glutamine; Intestinal Mucosa; Kidney; Kidney Tubules; Mitochondria; Physical Exertion

Fluid condensed from the breath of patients with acute asthma is acidic. Several features of asthma pathophysiology can be initiated by exposure of the airway to acid. In renal tubular epithelium, glutaminase produces ammonia to buffer urinary acid excretion. We hypothesized that human airway epithelium could also express glutaminase. Here, we demonstrate that human airway epithelial cells in vitro have biochemical evidence for glutaminase activity and express mRNA for two glutaminase isoforms (KGA and GAC). Glutaminase activity increased in response to acidic stress (media pH 5.8) and was associated with both increased culture medium pH and improved cell survival. In contrast, activity was inhibited by interferon-gamma and tumor necrosis factor-alpha. Glutaminase protein was expressed in the human airway in vivo. Further, ammonia levels in the breath condensate of subjects with acute asthma were low (30 microM [range: 0-233], n = 18, age 23 +/- 2.5 yr) compared with control subjects (327 microM [14-1,220], n = 24, age 24 +/- 2.4 yr, p < 0.001), and correlated with condensate pH (r = 0.58, p < 0.001). These data demonstrate that glutaminase is expressed and active in the human airway epithelium and may be relevant both to the regulation of airway pH and to the pathophysiology of acute asthmatic airway inflammation.

Topics: Acute Disease; Adult; Ammonia; Analysis of Variance; Asthma; Biopsy; Blotting, Western; Breath Tests; Case-Control Studies; Cell Survival; Gene Expression Regulation; Glutaminase; Humans; Hydrogen-Ion Concentration; Immunohistochemistry; Inflammation; Interferon-gamma; Isomerism; Respiratory Mucosa; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tumor Necrosis Factor-alpha; Up-Regulation

Previous studies have documented an increase in hepatic plasma membrane glutamine transport in the tumor-bearing rat, but the effects of tumor burden on hepatic glutaminase expression have not been carefully studied. The purpose of this study was to examine the effects of tumor burden and food intake on hepatic glutaminase expression. Rats were implanted with syngeneic methylcholanthrene-induced fibrosarcoma tumor tissue; control rats were sham operated and pair-fed every 24 hr. Northern blotting was used to assay the effect of tumor burden and fasting on hepatic glutaminase mRNA levels, using beta-actin mRNA as a control. Hepatic glutaminase mRNA levels in livers of pair-fed controls were found to be 4-fold greater than levels in livers of tumor-bearing animals. Examination of food intake patterns in these animals indicated that pair-fed controls ate their allotted chow quickly while tumor-bearing rats ate small amounts throughout each 24 hr period. This observation suggested that the differences in glutaminase mRNA levels may be due to a period of fasting by pair-fed animals which was not experienced by the tumor-bearing group. Hepatic glutaminase mRNA levels rapidly increased in normal rats during acute fasting to levels 5.5-fold greater than fed animals. Glucose feeding and insulin injection rapidly reversed the effect of fasting on hepatic glutaminase mRNA levels in normal rats. Tumor-bearing rats also exhibited upregulation of hepatic glutaminase mRNA levels in response to fasting.. (1) Tumor burden itself does not alter hepatic glutaminase expression, at least at the pre-translational level. Instead, differences in hepatic glutaminase mRNA content are due to differences in food intake patterns. (2) Hepatic glutaminase mRNA levels are rapidly upregulated in response to fasting, an effect which appears to be linked to a decrease in plasma insulin concentrations. Because tumor-bearing rats eat regularly over a 24 hr period (albeit in small increments), thereby maintaining the plasma insulin concentration, hepatic glutaminase mRNA may not rise as it does in pair-fed controls whose daily chow intake is complete within hours of food allocation. (3) This study indicates that differences in the timing of food intake between tumor-bearing rats and pair-fed controls can alter the expression of genes that are influenced by nutrient availability. These differences should be taken into account when designing studies which involve pair-feeding to control nutrient intake.

Topics: Acute Disease; Animals; Fibrosarcoma; Gene Expression; Glucose; Glutaminase; Insulin; Liver; Male; Methylcholanthrene; Neoplasm Transplantation; Rats; Rats, Inbred F344; Starvation

Phosphate-dependent glutaminase (PDG) was measured in kidney cortex homogenates and mitochondria from control and acutely acidotic rats. The effect of plasma from acutely acidotic rats on PDG activity in homogenates from normal rats was also studied. Acidosis or incubation in acidotic plasma enhanced enzyme activity when measured at 1.0 mM but not at 20.0 mM glutamine. This effect was not due to increased mitochondrial permeability since similar results were obtained after solubilization of the enzyme with Triton X-100. Increased enzyme activity was observed with either the Tris (monomer) form or the borate (polymer) form of the enzyme, indicating that enhanced activity is not due to polymerization but probably to a conformational change in the enzyme such that the Km for glutamine is lowered.

Topics: Acidosis; Acute Disease; Animals; Enzyme Activation; Glutaminase; Glutamine; Kidney Cortex; Kinetics; Male; Mitochondria; Polymers; Rats; Rats, Inbred Strains

Topics: Acidosis; Acute Disease; Adaptation, Physiological; Ammonia; Animals; Bicarbonates; Chronic Disease; Female; Glutaminase; Kidney; Phosphates; Rats

1. Slices of duodenum and jejunum produce ammonia from glutamine in vitro. 2. Ammoniagenesis does not increase in response to acidosis or potassium deficiency, two conditions known to cause enhanced ammoniagenesis in the kidney. 3. Gut contains glutaminase 1 as well as gamma-glutamyl transpeptidase. 4. These enzymes do not show any increase during starvation.

Topics: Acidosis; Acute Disease; Ammonia; Animals; Chronic Disease; Duodenum; gamma-Glutamyltransferase; Glutaminase; Glutamine; In Vitro Techniques; Intestine, Small; Jejunum; Organ Specificity; Rats; Starvation

Topics: Acute Disease; Animals; Brain; Brain Chemistry; Disease Models, Animal; Female; Glutamate-Ammonia Ligase; Glutaminase; Glutamine; Hypoxia, Brain; Rabbits; Transaminases

Topics: Acute Disease; Asparaginase; Cytarabine; Daunorubicin; Glutaminase; Humans; Leukemia; Leukemia, Myeloid; Vinblastine; Vincristine

Topics: Acute Disease; Amino Acids; Animals; Asparaginase; Blood; Body Weight; Chromatography, Ion Exchange; Chronic Disease; Diet; Escherichia coli; Female; Glutaminase; Glutamine; L-Lactate Dehydrogenase; Leukemia, Experimental; Mice; Neoplasm Transplantation; RNA Viruses; Virus Diseases