Glutamine-synthesizing activity in lungs of fed, starved, acidotic, diabetic, injured and septic rats.
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ABSTRACT:
SUBMITTER: Ardawi MS
PROVIDER: S-EPMC1131809 | biostudies-other | 1990 Sep
REPOSITORIES: biostudies-other
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Project description:A newly developed specific radioimmunoassay was used to quantify phosphofructokinase protein directly and independently of assayable activity in liver and kidney cytosol of normal fed, starved and alloxan-diabetic rats. In the fed state, liver phosphofructokinase concentration was 0.096 microM and the kidney enzyme was 0.086 microM (mumol/kg of tissue). In the starved state (24h), liver and kidney phosphofructokinase concentrations decreased by 30%. Prolonged starvation up to 72h did not further decrease enzyme concentration. In liver, total enzyme content during starvation declined by more than 50%, secondary also to a decrease in liver weight. In the alloxan-diabetic rats, there was a 22% decrease in enzyme protein concentration in liver and kidney. Total enzyme content per liver actually decreased much more (46%), because diabetes also resulted in a decrease in liver size. In conjunction with assayable activity measurements, the results of the radioimmunoassay allowed us to calculate the apparent specific activity of the enzyme. The specific activity of the kidney enzyme was 2-3 times that of the liver. Little or no change in specific activity of the liver or kidney enzyme occurred as a result of starvation or chemically induced diabetes. Tissue enzyme concentrations of phosphofructokinase unequivocally reconcile the ultimate results of changing rates of synthesis and degradation and are useful data in the design of spectrophotometric, kinetic, aggregation-disaggregation and other studies.
| S-EPMC1144463 | biostudies-other
Project description:The rate of leucine C-2 incorporation into glutamine was compared in control and septic rats. Female Sprague-Dawley rats (n = 46, 210-260 g) were fed parenterally for 3 days and then randomized into two groups (control and septic). Sepsis was induced by the injection of 10(10) live Escherichia coli/kg on day 4 into the septic group. Rats in each group were given a continuous (8 h) infusion of one of three different isotopes. The isotopes were given 24 h after inoculation. Leucine oxidation and incorporation into protein were determined with [1-13C]leucine; glutamine flux and oxidation were determined with [5-13C]glutamine, and the fraction of leucine C-2 incorporated into glutamine was determined by giving [1,2-13C]leucine. Results were as follows: sepsis caused a significant increase in the rate of leucine C-2 incorporation into glutamine (66.0 +/- 3.7 as against 29.6 +/- 3.7 mumol/h per kg, P less than 0.01). This increase was due to both an increase in glutamine production (2331 +/- 76 as against 1959 +/- 94 mumol/h per kg, P less than 0.01) and an increase in the proportion of glutamine derived from leucine (2.83 +/- 0.27% as against 1.51 +/- 0.31%, P less than 0.01). The ratio of leucine C-2 incorporated into glutamine to leucine oxidized increased from 7.16 +/- 0.91% to 11.49 +/- 1.12% with sepsis (P less than 0.05).
| S-EPMC1151106 | biostudies-other
Project description:Hepatic carnitine palmitoyltransferase (CPT) turnover was studied in control and in non-ketotic hyperglycaemic streptozotocin-diabetic rats. The degradation constant (kd) and half-life (t1/2) did not appear to be altered by mild diabetes. The hepatic CPT (micrograms/g of liver) was not increased by the mild, non-ketotic, diabetes. However, the total hepatic CPT (micrograms/liver) was 37% greater in the diabetic animals, owing to the increased liver weight. This resulted from a 40% increase in the synthesis constant (ks). Hepatic CPT activity (total detergent-solubilized) and translation rates were measured in fed, starved (48 h), non-ketotic diabetic, ketotic diabetic and diethylhexyl phthalate (DEHP)-treated rats. CPT activity (m units/mg of mitochondrial protein) was not significantly increased with non-ketotic diabetes (44% increase, but non-significant), but was increased approx. 2-fold with starvation and ketotic diabetes, and 3.5-fold with DEHP treatment. CPT expressed as units/liver was increased non-significantly (23%) in non-ketotic and starved rats, similar to the turnover study, but was significantly increased with ketotic diabetes and with DEHP treatment. mRNA-translation activity for CPT was elevated in all states to a somewhat greater extent than was activity. It was concluded that protein synthesis as a product of increased CPT-mRNA translation activity is a major means of long-term regulation.
| S-EPMC1148328 | biostudies-other
Project description:The turnover of glutamine was measured in rats with [1-14C]glutamine. Rates of turnover measured by constant infusion of the label were 130 mumol/h per 100g body wt. in control rats and were not changed in chronic metabolic acidosis. These rates of turnover of whole-body glutamine were about 13-26% of the rate of net glutamine release into the bloodstream, indicating that the bulk of glutamine turnover in vivo is concerned with intracellular processes rather than inter-organ fluxes.
| S-EPMC1154217 | biostudies-other
Project description:1. Rats were starved for 48hr. or fed for 1 week on a high-fat or a high-carbohydrate diet. The effects of these dietary alterations on the rate of production of (14)CO(2) from trace amounts of [U-(14)C]glucose, [1-(14)C]palmitate or [1-(14)C]acetate administered intravenously were studied. 2. The oxidation of [(14)C]glucose was most rapid in the carbohydrate-fed condition and was decreased significantly and to the same extent after starvation and after feeding with fat. 3. Under all dietary regimes studied the maximum rate of elimination of (14)CO(2) from [(14)C]palmitate occurred within a few minutes after injection, but considerably more was oxidized after starvation and feeding with fat than after feeding with carbohydrate. 4. Alterations in diet had no effect on the oxidation and high recovery of administered [(14)C]acetate as (14)CO(2). 5. Graphical analysis showed the presence of several exponential components in the (14)CO(2)-elimination curves. 6. In all studies a marked similarity in oxidative pattern was noted between the starved and the fat-fed rat.
| S-EPMC1270421 | biostudies-other
Project description:The mechanism of activation of glutamine production by the hindlimb during diabetic ketoacidosis (DKA) was investigated in rats. Muscle glutamine production was estimated to account for over 90% of the total glutamine produced by the hindlimb. DKA produced significant increases in the concentrations of NH4+ and IMP in hindlimb muscles, suggesting that AMP deaminase is activated by DKA. NH4Cl- and HCl-induced acidosis did not produce these changes, indicating either that acidosis itself is not the stimulus for increased AMP deaminase activity or that the more severe degree of acidosis accompanying DKA is necessary for activation. Muscle glutamine concentrations were depressed in DKA. Experiments with isolated epitrochlearis muscle showed that the transport and permeability properties of the muscle cells (as judged by uptake and release of alpha-aminoisobutyrate and glutamine) were not altered by DKA. However, glutamine uptake by muscle cells was significantly inhibited by L-leucine, the concentration of which, along with other branched-chain amino acids, is markedly elevated in DKA.
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Project description:1. When isolated kidneys from fed rats were perfused with glutamine the rate of ammonia release at pH7.4 (110-360mumol/h per g dry wt.) was one to two times that of glutamine removal. Glucose formation from 5mm-glutamine was 16mumol/h per g. If kidneys were perfused with glutamine at pH7.1 (10-13mm-sodium bicarbonate) there was no increase in glutamine removal or in the formation of ammonia or glucose. 2. When isolated kidneys from fed rats were perfused with glutamate at pH7.4, glucose formation was 59mumol/h per g, glutamine formation was 182mumol/h per g and ammonia release was negligible. At pH7.1 glutamine synthesis was inhibited and formation of ammonia and glucose were increased. 3. In perfused kidneys from acidotic rats, which had received 1.5% (w/v) NH(4)Cl to drink for 7-10 days, gluconeogenesis from glutamine was enhanced (101mumol/h per g). Glutamine removal and ammonia formation were also increased, compared with the rates in perfused kidney from normal rats. The extra glutamine consumed was equivalent to the extra glucose formed. 4. When the kidney from the 7-10-day-acidotic rat was perfused with glutamate gluconeogenesis was increased (113mumol/h per g). Synthesis of glutamine was decreased, and ammonia release was approximately equal to the rate of glutamate removal. 5. The time-course of these metabolic alterations was investigated after the rapid induction of acidosis by infusion of 0.25m-HCl into the right side of the heart. The increase in gluconeogenesis from glutamine developed gradually over several hours. When kidneys from 6h-acidotic rats were perfused with glutamate, formation of glucose and glutamine were both rapid. 6. In acidotic rat kidneys perfused with glutamine, tissue concentrations of glutamate and glucose 6-phosphate were increased compared with those in control perfused kidneys from non-acidotic rats. 7. The results are discussed in terms of control of the renal metabolism of glutamine. In particular, it is suggested that in acidotic rats glucose formation is the major fate of the carbon of the extra glutamine utilized by the kidney, and that inhibition of glutamine synthetase could contribute to the increase in intracellular ammonia concentration in the kidney.
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Project description:1. The oxidation of glutamine by kidney-cortex mitochondria from normal and acidotic rats was not inhibited by avenaciolide, which did inhibit glutamate uptake and oxidation. The oxidation of glutamine by these mitochondria was always greater than that of glutamate. Direct measurements of the metabolism of [1-14C]glutamine in the presence of glutamate, and of [1-14C]glutamate in the presence of glutamine, demonstrated that the uptake and metabolism of external glutamate is insufficient to account for the observed rate of glutamine uptake and metabolism. Thus the postulated glutamine/glutamate antiport does not play a quantitatively important role in the metabolism of glutamine by renal mitochondria. 2. Rapid swelling of these mitochondria was observed in iso-osmotic solutions of L-glutamine and L-glutamyl-gamma-monohydroxamate but not in D-glutamine or L-isoglutamine (1-amido-2-aminoglutaric acid). Thus a relatively specific glutamine uniport exists in these mitochondria. 3. The utilization of glutamine was increased about 3-fold in mitochondria from chronically acidotic rats. Thus mitochondrial adaptations play an important part in the renal response to metabolic acidosis.
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Project description:The co-operation of specialized organ systems in complex multicellular organisms depends on effective chemical communication. Thus, body fluids (like blood, lymph or intraspinal fluid) contain myriads of signaling mediators apart from metabolites. Moreover, these fluids are also of crucial importance for immune and wound responses. Compositional analyses of human body fluids are therefore of paramount diagnostic importance. Further improving their comprehensiveness should increase our understanding of inter-organ communication. In arthropods, which have trachea for gas exchange and an open circulatory system, the single dominating interstitial fluid is the hemolymph. Accordingly, a detailed analysis of hemolymph composition should provide an especially comprehensive picture of chemical communication and defense in animals. Therefore we used an extensive protein fractionation workflow in combination with a discovery-driven proteomic approach to map out the detectable protein composition of hemolymph isolated from Drosophila larvae. Combined mass spectrometric analysis revealed more than 700 proteins extending far beyond the previously known Drosophila hemolymph proteome. Moreover, by comparing hemolymph isolated from either fed or starved larvae, we provide initial provisional insights concerning compositional changes in response to nutritional state. Storage proteins in particular were observed to be strongly reduced by starvation. Our hemolymph proteome catalog provides a rich basis for data mining, as exemplified by our identification of potential novel cytokines, as well as for future quantitative analyses by targeted proteomics.
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Project description:The fructose 2,6-bisphosphate (Fru-2,6-P2) content and intracellular concentration of lactating mammary gland was measured in fed, starved and re-fed rats. There was little or no change on starvation, and about 1.5-fold rise on re-feeding, contrasting with estimated glycolytic changes of about 10-fold. The 6-phosphofructokinase (PFK-1) activity of mammary extracts was highly sensitive to added Fru-2,6-P2 under all conditions examined, and appeared to approach saturation at physiological concentrations of this effector. The activity of mammary PFK-1 measured under optimal and 'physiological' conditions suggested that this enzyme operates in vivo at about 24% of maximal rate, and is likely to be an important rate-limiting factor in mammary glycolysis.
| S-EPMC1152973 | biostudies-other