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PubMed1981

Liver metabolites in resting and exercising rats at 1 and 4 bar.

Groups of six rats were put into a compression chamber and exposed to an air pressure of 4 bar or remained at 1 bar. Half of each group was forced to swim in a tank of warm water; the other half remained at rest. A total of 28 rats was used. After 30 min the rats were killed, and part of the liver was rapidly (less than 10 s) removed and pressed between metal plates that had been cooled in liquid nitrogen. Analyses of the metabolites indicated a significant reduction gluconeogenesis in the animals exercising under pressure, probably due to a diminished return of substrates from the muscles. There also appeared to be the possibility of enzymatic control between fructose 6-phosphate and the triose phosphates.

Air Pressure↗
PubMedDate not supplied

Ammonia production from hippurate by the rat kidney in vitro.

Hippurate is known to be synthesized from benzoate and glycine in the liver and kidney. It takes part in renal ammoniagenesis by modulating the activity of gamma-glutamyl transpeptidase (gamma GT). Due to its chemical structure, however, hippurate might also serve as a substrate of renal ammoniagenesis. Hippurate may yield ammonia either having been cleaved by hippuricase or by Erlenmeyer's reaction after condensation with an aldehyde. In order to elucidate the possibility of hippurate being a substrate of renal ammoniagenesis, experiments were carried out on cortical kidney slices and on isolated tubular segments of the rat. The incubation medium (pH 7.1) was enriched with 10 mmol/l hippurate spiked with 15N-hippurate, some of the known competitive inhibitors of hippuricase, acivicin and different aldehydes. Factors known to affect hippuricase or gamma GT did not interfere with renal ammonia production. Glyceraldehyde (up to 1.0 mmol/l) but not glycerate had a stimulating effect, especially on the ammoniagenesis from hippurate. In normal rats fed a vegetarian diet, 1% of the added 15N moiety was found to be 15NH3. Renal 15NH3 production was significantly greater if, prior to the experiments, the animals were either acidotic or had a reduced renal mass or were fed animal proteins. These results indicate that hippurate may, to a certain extent, serve as substrate for ammoniagenesis.

Acidosis, Renal Tubular↗
PubMed1970

The effects of deoxygenation of adult and fetal hemoglobin on the synthesis of red cell 2,3-diphosphoglycerate and its in vivo consequences.

Patients over 1 month of age with arterial oxygen pressures of less than 60 mm Hg were found to have elevated red cell 2,3-diphosphoglycerate (2,3-DPG) levels and blood with a decreased affinity for oxygen. The increase in 2,3-DPG was proportional to the degree of hypoxemia. In patients under 1 month of age this relationship was not observed. Red cells from adults, but not newborns, showed rapid increases in 2,3-DPG when incubated under nitrogen. Adult, but not fetal, deoxyhemoglobin was shown to facilitate in vitro synthesis of 2,3-DPG by binding this organic phosphate and relieving the product inhibition of 2,3-DPG mutase. Throughout a wide range change in oxygen affinity as measured by the P(50) is linear with respect to the 2,3-DPG concentration; a change of 430 mmumoles of 2,3-DPG/ml of red blood corpuscles (RBC) resulting in a change of the P(50) of 1 mm Hg. It appears that the 2,3-DPG of the adult's red cells responds rapidly to metabolic and environmental influences and in turn effects metabolism and the cellular environment. Many of these effects are not shared by the red cells of the newborn.

Adolescent↗
PubMed1972

Energy metabolism in human erythrocytes. II. Effects of glucose depletion.

Normal red cells were incubated in the absence of glucose to develop a system in which total adenosine triphosphate (ATP) turnover could be assessed. After 1 hr, the triose pool had been completely consumed. Thereafter, the metabolism of 2,3-diphosphoglycerate (DPG) to pyruvate and lactate was the sole significant source of ATP synthesis.10(-3)M CuCl(2), which did not enter the cells, diminished ATP utilization by more than 50%. This could be only partially attributed to the inhibition by copper of residual acylation and cation pumping, which were already reduced by glucose depletion. Other membrane enzymes, which presumably function in the maintenance of membrane integrity, must, therefore, use a significant portion of erythrocyte ATP. The behavior of glucose-depleted red cells with respect to cation transport was complex. The addition of ouabain did not decrease ATP utilization in these red cells. Ouabain inhibitable potassium influx was nearly normal after triose depletion, but total potassium influx was decreased. In contrast, the ouabain inhibitable sodium efflux was markedly reduced after triose depletion, although the concentration of ATP was 70% of normal. The dissociation of monovalent cation pumping suggests that the energy for active sodium transport is derived from a specific source (such as the ATP produced by the phosphoglycerate kinase reaction) distinct from that for potassium transport.

Adenosine Triphosphate↗
PubMed2006

Oxalate enhances protein synthesis in cell-free synthesis system utilizing 3-phosphoglycerate as energy source.

Herein, we report our results showing that the productivity of cell-free protein synthesis can be enhanced through the regulation of the in vitro metabolism of an energy source. In a reaction mixture utilizing 3-phosphoglycerate (3PG) as an energy source, the supply of ATP was significantly enhanced when the reaction mixture was supplied with sodium oxalate, a potent inhibitor of phosphoenolpyruvate synthetase (PPS). The productivity of protein synthesis was also increased by approximately 70% upon the addition of oxalate. It was presumed that this enhancement in ATP supply resulted from the prevention of the pyruvate --> PEP reaction, which causes nonproductive ATP consumption. For the initial presence of 2.1 mM sodium oxalate, approximately 720 microg/ml chloramphenicol acetyltransferase (CAT) was produced after 3 h of incubation at 37 degrees C.

Adenosine Triphosphate↗
PubMed1975

Distribution studies of glycine and serine enzymes in chicks.

Day-old broiler type chicks were fed a practical starter ration for three weeks, sacrificed and the D-3-phosphoglycerate dehydrogenase (E.C.1.1.1.s), phosphoserine phosphatase (E.C.3.1.3.3.), glycerate dehydrogenase (E.C.1.1.1.29), hydroxypyruvate-P: glutamate transaminase, serine transhydroxymethylase (E.C.2.1.2.1), and serine dehydratase (E.C.4.2.1.13) enzyme activities were determined in liver, kidney, heart, spleen and brain tissue in evaluating glycine and serine metabolism. The distribution of the various glycine and serine biosynthetic enzymes in the chick tissues studied show that the major portion of glycine and serine synthesis occurs in hepatic tissue via the "phosphorylated pathway".

Alcohol Oxidoreductases↗