The effect of phenobarbitone on protein synthesis by liver polyribosomes in fed and starved rats.
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ABSTRACT:
SUBMITTER: Ragnotti G
PROVIDER: S-EPMC1165269 | biostudies-other | 1975 Jan
REPOSITORIES: biostudies-other
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Project description:1. The influence of ethanol on the metabolism of livers from fed and starved rats has been studied in liver-perfusion experiments. Results have been obtained on oxygen consumption and carbon dioxide production, on glucose release and uptake by the liver and on changes in the concentrations of lactate and pyruvate and of beta-hydroxybutyrate and acetoacetate in the perfusion medium. 2. Oxygen consumption and carbon dioxide production were lower in livers from starved rats than in livers from fed rats. Ethanol had no effect on the oxygen consumption of either type of liver. After the addition of ethanol to the perfusion medium carbon dioxide production ceased almost completely, the change being faster in livers from starved rats. 3. With livers from fed rats glucose was released from the liver into the perfusion medium. This release was slightly greater when ethanol was present. With livers from starved rats no release of glucose was observed, and when ethanol was added a marked uptake of glucose from the medium was found. A simultaneous release of glycolytic end products, lactate and pyruvate, into the medium occurred. 4. Acetate was the main metabolite accumulating in the perfusion medium when ethanol was oxidized. With livers from starved rats a slightly increased formation of ketone bodies was found when ethanol was present. 5. The lactate/pyruvate concentration ratio in the perfusion medium increased from 10 to 87 with livers from fed rats and from 20 to 171 with livers from starved rats when the livers were perfused with ethanol in the medium. The beta-hydroxybutyrate/acetoacetate concentration ratio increased from 0.8 to 7.6 with livers from fed rats and from 1.0 to 9.5 with livers from starved rats when ethanol was added to the medium. 6. The effects of ethanol are discussed and related to changes in the redox state of the liver that produce new conditions for some metabolic pathways.
| S-EPMC1206436 | biostudies-other
Project description:Liver content of pentose-cycle intermediates and the activity of the three major cytoplasmic NADPH-producing enzymes and pentose-cycle enzymes were measured in three dietary states: 48 h-starved rats, rats fed on a standard diet ad libitum, and rats meal-fed with a low-fat high-carbohydrate diet. Measured tissue contents of pentose-cycle intermediates in starved liver were: 6-phosphogluconate, 4.7 +/- 0.5 nmol/g; ribulose 5-P, 3.7 +/- 0.5 nmol/g; xylulose 5-P, 4.3 +/- 0.4 nmol/g; sedoheptulose 7-P, 25.5 +/- 1.3 nmol/g; and combined sedoheptulose 7-P and ribose 5-P, 30.6 +/- 0.7 nmol/g. These values were in good agreement with values calculated from fructose 6-P and free glyceraldehyde 3-P, assuming the major transketolase, transaldolase, ribulose-5-P 3-epimerase and ribose-5-P isomerase reactions were all in near-equilibrium. Similar results were found in animals fed ad libitum. These relationships were not valid in animals fed on a low-fat high-carbohydrate diet, with tissue contents of metabolites in some cases being more than an order of magnitude higher than the calculated values. Measured tissue contents of pentose-cycle intermediates in these animals were: 6-phosphogluconate, 124.2 +/- 13.9 nmol/g; ribulose 5-P, 44.8 +/- 7.1 nmol/g; xylulose 5-P, 77.2 +/- 9.4 nmol/g; sedoheptulose 7-P, 129.9 +/- 10.1 nmol/g; and combined sedoheptulose 7-P and ribose 5-P, 157.0 +/- 11.3 nmol/g. In all animals, regardless of dietary state, tissue content of erythrose 4-P was less than 2 nmol/ml. Liver activities of glucose-6-P dehydrogenase and 6-phosphogluconate dehydrogenase were increased from 3.5 +/- 0.9 mumol/g and 7.3 +/- 0.5 mumol/min per g in starved animals to 13.2 +/- 1.1 and 10.5 +/- 0.7 mumol/min per g in low-fat high-carbohydrate-fed animals. Despite these changes, the activities of transaldolase (3.4 +/- 0.3 mumol/min per g), transketolase (7.8 +/- 0.2 mumol/min per g) and ribulose-5-P 3-epimerase (7.5 +/- 0.4 mumol/min per g) were not increased in meal-fed animals above those observed in starved animals (3.4 +/- 0.2, 7.1 +/- 0.3 and 8.6 +/- 0.4 mumol/min per g respectively). The increase in the activity of oxidative pentose-cycle enzymes in the absence of any change in the non-oxidative pentose cycle appeared to contribute to the observed disequilibrium in the pentose cycle in animals meal fed on a low-fat high-carbohydrate diet.
| S-EPMC1146893 | 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: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:1. The rate of protein synthesis in rat tissues was measured by constant intravenous infusion of [(14)C]tyrosine. A modification has been developed for the method of calculating the rate of protein synthesis in individual tissues from the specific radioactivity of the free and protein-bound amino acid in tissue at the end of the infusion. This technique gives greater accuracy and allows a greater choice of labelled amino acids. The specific radioactivity of free tyrosine in plasma was used to calculate the plasma tyrosine flux, an index of the rate of protein synthesis in the whole body. 2. Young male Wistar rats were allowed access to food for only 4h in every 24h. The tyrosine flux and the rate of protein synthesis in liver and muscle at different periods of time after a single feed were estimated. 3. The tyrosine flux did not alter after feeding nor even after starvation for 48h. 4. The average fractional rate of protein synthesis in muscle was 7.2%/day, i.e. the proportion of the protein mass which is replaced each day. The rate rose after eating and declined during starvation for 48h. In addition the rate of muscle protein synthesis correlated with the growth rate of the rat. 5. In liver the average fractional rate of protein synthesis was 50%/day. There was no change in the rate after eating nor after starvation for 48h. In contrast with muscle this suggests that the changes in protein mass were accompanied by changes in the rate of protein breakdown rather than synthesis.
| S-EPMC1166043 | biostudies-other
Project description:The metabolism of [2-3H]lactate was studied in isolated hepatocytes from fed and starved rats metabolizing ethanol and lactate in the absence and presence of fructose. The yields of 3H in ethanol, water, glucose and glycerol were determined. The rate of ethanol oxidation (3 mumol/min per g wet wt.) was the same for fed and starved rats with and without fructose. From the detritiation of labelled lactate and the labelling pattern of ethanol and glucose, we calculated the rate of reoxidation of NADH catalysed by lactate dehydrogenase, alcohol dehydrogenase and triosephosphate dehydrogenase. The calculated flux of reducing equivalents from NADH to pyruvate was of the same order of magnitude as previously found with [3H]ethanol or [3H]xylitol as the labelled substrate [Vind & Grunnet (1982) Biochim. Biophys. Acta 720, 295-302]. The results suggest that the cytoplasm can be regarded as a single compartment with respect to NAD(H). The rate of reduction of acetaldehyde and pyruvate was correlated with the concentration of these metabolites and NADH, and was highest in fed rats and during fructose metabolism. The rate of reoxidation of NADH catalysed by lactate dehydrogenase was only a few per cent of the maximal activity of the enzymes, but the rate of reoxidation of NADH catalysed by alcohol dehydrogenase was equal to or higher than the maximal activity as measured in vitro, suggesting that the dissociation of enzyme-bound NAD+ as well as NADH may be rate-limiting steps in the alcohol dehydrogenase reaction.
| S-EPMC1144197 | biostudies-other
Project description:We have used the cold-clamping technique to study the changes in acetyl-CoA carboxylase activity that occur in the cytosolic and mitochondrial fractions of the liver of fed, starved and starved-refed rats. No evidence was found for a role of the mitochondrial enzyme as a pool from which cytosolic carboxylase could be replenished upon refeeding of starved rats. Starvation for 24 h or 48 h induced changes in the expressed (assayed at 20 mM-citrate), total (citrate- and phosphatase-treated) and citrate-independent activities of cytosolic carboxylase, as well as in its Ka for citrate. The expressed/total activity ratio was low even in the fed state and was depressed further by starvation. The effects of refeeding occurred in two phases: an acute phase (approx. 1 h) in which the starvation-induced changes in Ka and expressed/total activity ratio were rapidly reversed, and a prolonged slow phase in which the two parameters attained values that were lower and higher, respectively, than those in the normal fed state. Refeeding also resulted in a gradual increase in citrate-independent activity of acetyl-CoA carboxylase. An additional marked increase in this activity occurred only in 48 h-starved-refed rats between 24 h and 48 h of refeeding. These findings are discussed in terms of the observed time courses of changes in lipogenic rates that occur in vivo in starved-refed rats and of the possible molecular mechanisms involved.
| S-EPMC1149730 | biostudies-other
Project description:BackgroundThis study investigated the protective effect of aplysin on the liver and its influence on inflammation and the gut microbiota in rats with ethanol-induced liver injury.MethodsMale Sprague-Dawley rats were randomly assigned to an alcohol-containing liquid diet, control liquid diet or treatment with aplysin for 8 weeks. Hepatic and intestinal histopathological analysis was performed, and cytokine levels and the intestinal mucosal barrier were assessed. Enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) and 16S rDNA high-throughput sequencing were performed to provide an overview of the gut microbiota composition.ResultsChronic alcohol exposure caused liver damage in rats. Serum aspartate aminotransferase (AST), aminotransferase (ALT), alkaline phosphatase (ALP) and triglyceride (TG) activities in liver tissue were higher than in the control group. Alcohol administration elevated the levels of serum transforming growth factor-β (TGF-β) and tumor necrosis factor-α (TNF-α) and reduced interleukin-10 (IL-10) levels compared with those of control rats. In addition, the levels of plasma endotoxin, diamine oxidase (DAO), and fatty acid-binding protein 2 (FABP2) in the alcohol group were higher than in the control group. The results of ERIC-PCR indicated that aplysin treatment shifted the overall structure of the ethanol-disrupted gut microbiota toward that of the control group. One hundred twenty to 190 genera of bacteria were detected by high throughput sequencing. Alcohol-induced changes in the gut microbial composition were detected at the genus level. These alcohol-induced effects could be reversed with aplysin treatment.ConclusionsThese results suggest that aplysin exerts a protective effect on ethanol-induced hepatic injury in rats by normalizing fecal microbiota composition and repairing intestinal barrier function.
| S-EPMC5473570 | biostudies-literature
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
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.
| S-EPMC3688620 | biostudies-literature