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1.
We used-escin-permeabilized pig cerebral microvessels (PCMV) to study theorganization of carbohydrate metabolism in the cytoplasm of vascularsmooth muscle (VSM) cells. We have previously demonstrated (Lloyd PGand Hardin CD. Am J Physiol Cell Physiol 277: C1250-C1262,1999) that intact PCMV metabolize the glycolytic intermediate[1-13C]fructose 1,6-bisphosphate (FBP) to[1-13C]glucose with negligible production of[3-13C]lactate, while simultaneouslymetabolizing [2-13C]glucose to[2-13C]lactate. Thus gluconeogenic andglycolytic intermediates do not mix freely in intact VSM cells(compartmentation). Permeabilized PCMV retained the ability tometabolize [2-13C]glucose to[2-13C]lactate and to metabolize[1-13C]FBP to[1-13C]glucose. The continued existence ofglycolytic and gluconeogenic activity in permeabilized cells suggeststhat the intermediates of these pathways are channeled (directlytransferred) between enzymes. Both glycolytic and gluconeogenic flux inpermeabilized PCMV were sensitive to the presence of exogenous ATP andNAD. It was most interesting that a major product of[1-13C]FBP metabolism in permeabilized PCMV was[3-13C]lactate, in direct contrast to ourprevious findings in intact PCMV. Thus disruption of the plasmamembrane altered the distribution of substrates between the glycolyticand gluconeogenic pathways. These data suggest that organization of theplasma membrane into distinct microdomains plays an important role insorting intermediates between the glycolytic and gluconeogenic pathwaysin intact cells. 相似文献
2.
Role of microtubules in the regulation of metabolism in isolated cerebral microvessels 总被引:1,自引:0,他引:1
Lloyd Pamela G.; Hardin Christopher D. 《American journal of physiology. Cell physiology》1999,277(6):C1250
We used13C-labeled substrates and nuclearmagnetic resonance spectroscopy to examine carbohydrate metabolism invascular smooth muscle of freshly isolated pig cerebral microvessels(PCMV). PCMV utilized[2-13C]glucose mainlyfor glycolysis, producing[2-13C]lactate.Simultaneously, PCMV utilized the glycolytic intermediate [1-13C]fructose1,6-bisphosphate (FBP) mainly for gluconeogenesis, producing[1-13C]glucose withonly minor[3-13C]lactateproduction. The dissimilarity in metabolism of[2-13C]FBP derivedfrom [2-13C]glucosebreakdown and metabolism of exogenous[1-13C]FBPdemonstrates that carbohydrate metabolism is compartmented in PCMV.Because glycolytic enzymes interact with microtubules, we disruptedmicrotubules with vinblastine. Vinblastine treatment significantlydecreased[2-13C]lactate peakintensity (87.8 ± 3.7% of control). The microtubule-stabilizing agent taxol also reduced[2-13C]lactate peakintensity (90.0 ± 2.4% of control). Treatment with both agentsfurther decreased[2-13C]lactateproduction (73.3 ± 4.0% of control). Neither vinblastine, taxol,or the combined drugs affected[1-13C]glucose peakintensity (gluconeogenesis) or disrupted the compartmentation ofcarbohydrate metabolism. The similar effects of taxol and vinblastine, drugs that have opposite effects on microtubule assembly, suggest thatthey produce their effects on glycolytic rate by competing withglycolytic enzymes for binding, not by affecting the overall assemblystate of the microtubule network. Glycolysis, but not gluconeogenesis,may be regulated in part by glycolytic enzyme-microtubule interactions. 相似文献
3.
Glucose metabolism and the channeling of glycolytic intermediates in permeabilized L-929 cells 总被引:1,自引:0,他引:1
L-929 cells (mouse fibroblasts) permeabilized with dextran sulfate (DSP cells) carry out vigorous and linear rates of glycolysis when supplied with a suitable incubation medium. Glycolysis in DSP cells is pH dependent, being strongly inhibited at pH 6.5. Compared to their nonpermeabilized counterparts, DSP cells exhibit faster glycolytic rates, but tend to convert a smaller proportion of the glucose utilized to lactate. [14C]Glucose is converted to lactate by DSP cells without dilution from endogenous substrates. When exogenous 12C-labeled glycolytic intermediates (12C-I) are added to glycolyzing DSP cells the [14C]lactate produced from [14C]glucose is diluted to varying extents, depending on the intermediate. However, the extent of that dilution (reduced specific activity) is not that expected from the complete mixing of exogenous 12C-I with their corresponding 14C-labeled intermediates coming from [14C]-glucose. DSP cells also respire and convert glucose to CO2. The amount of 14CO2 produced from [14C]glucose is also reduced by addition of most 12C-I, an interesting exception being pyruvate, which had no measurable effect on 14CO2 production and caused only a modest stimulation of respiration in glycolyzing DSP cells. These results suggest that channeling, or some other form of coupling, takes place between the glycolytic production of pyruvate and its further oxidation. These observations confirm previously published data and add further support to the proposition that channeling of glycolytic intermediates occurs in DSP cells but is of the "leaky" type. Although abundant evidence in the literature indicates that various glycolytic enzymes associate with F-actin, as well as other elements of the cytomatrix, we observed no effect of cytochalasin D on lactate production even at very high concentrations of this compound. Our results are compared with those from other laboratories and discussed in the context of metabolic organization. 相似文献
4.
Halseth Amy E.; Bracy Deanna P.; Wasserman David H. 《Journal of applied physiology》1998,85(6):2305-2313
The hypothesisof this investigation was that insulin and muscle contraction, byincreasing the rate of skeletal muscle glucose transport, would biascontrol so that glucose delivery to the sarcolemma (and t tubule) andphosphorylation of glucose intracellularly would exert more influenceover glucose uptake. Because of the substantial increases in blood flow(and hence glucose delivery) that accompany exercise, we predicted thatglucose phosphorylation would become more rate determining duringexercise. The transsarcolemmal glucose gradient (TSGG; the glucoseconcentration difference across the membrane) is inversely related tothe degree to which glucose transport determines the rate of glucoseuptake. The TSGG was determined by using isotopic methods in consciousrats during euglycemic hyperinsulinemia [Ins; 20 mU/(kg · min); n = 7], during treadmill exercise (Ex,n = 6), and in sedentary,saline-infused rats (Bas, n = 13).Rats received primed, constant intravenous infusions of trace3-O-[3H]methyl-D-glucoseand [U-14C]mannitol.Then2-deoxy-[3H]glucosewas infused for the calculation of a glucose metabolic index(Rg). At the end of experiments,rats were anesthetized, and soleus muscles were excised. Total soleusglucose concentration and the steady-state ratio of intracellular toextracellular3-O-[3H]methyl-D-glucose(which distributes on the basis of the TSGG) were used to calculateranges of possible glucose concentrations ([G]) at theinner and outer sarcolemmal surfaces([G]im and[G]om, respectively).Soleus Rg was increased in Ins andfurther increased in Ex. In Ins, total soleus glucose,[G]om, and the TSGGwere decreased compared with Bas, while[G]im remained near 0. In Ex, total soleus glucose and[G]im were increasedcompared with Bas, and there was not a decrease in[G]om as was observedin Ins. In addition, accumulation of intracellular free2-deoxy-[3H]glucoseoccurred in soleus in both Ex and Ins. Taken together, these dataindicate that, in Ex, glucose phosphorylation becomes an importantlimitation to soleus glucose uptake. In Ins, both glucose delivery andglucose phosphorylation influence the rate of soleus glucose uptakemore than under basal conditions. 相似文献
5.
Peronnet F.; Burelle Y.; Massicotte D.; Lavoie C.; Hillaire-Marcel C. 《Journal of applied physiology》1997,82(2):440-446
Péronnet, F., Y. Burelle, D. Massicotte, C. Lavoie,and C. Hillaire-Marcel. Respective oxidation of13C-labeled lactate and glucoseingested simultaneously during exercise. J. Appl.Physiol. 82(2): 440-446, 1997.The purpose ofthis experiment was to measure, by using13C labeling, the oxidation rateof exogenous lactate (25 g, as Na+,K+,Ca2+, andMg2+ salts) and glucose (75 g)ingested simultaneously (in 1,000 ml of water) during prolongedexercise (120 min, 65 ± 3% maximum oxygen uptake in 6 male subjects). The percentage of exogenous glucose and lactateoxidized were similar (48 ± 3 vs. 45 ± 5%, respectively). However, because of the small amount of oral lactate that could be tolerated without gastrointestinal discomfort, the amountof exogenous lactate oxidized was much smaller than that of exogenousglucose (11.1 ± 0.5 vs. 36.3 ± 1.3 g, respectively) andcontributed to only 2.6 ± 0.4% of the energy yield(vs. 8.4 ± 1.9% for exogenous glucose). The cumulative amount ofexogenous glucose and lactate oxidized was similar to that observedwhen 100 g of[13C]glucose wereingested (47.3 ± 1.8 vs. 50.9 ± 1.2 g, respectively). When[13C]glucose wasingested, changes in the plasma glucose13C/12Cratio indicated that between 39 and 61% of plasma glucose derived fromexogenous glucose. On the other hand, the plasma glucose 13C/12Cratio remained unchanged when[13C]lactate wasingested, suggesting no prior conversion into glucose before oxidation. 相似文献
6.
We evaluated the applicability of stableisotopic tracers to the study of intramuscular fatty acid metabolism byinfusing both[U-13C]palmitateand [1-13C]oleateintravenously for 4 h into fasted conscious rats. Skeletal muscles weresequentially biopsied, and the concentration and 13C enrichment of fatty acids weremeasured by gas chromatography/combustion/isotope ratio massspectrometry. Throughout the study, the13C enrichment of plasma palmitateand oleate remained substantially greater than intramuscularnonesterified palmitate and oleate enrichment, which in turn wasgreater than intramuscular triglyceride palmitate and oleateenrichment. Fractional synthesis rates of intramuscular triglyceridesin gastrocnemius and soleus were 0.267 ± 0.075 and 0.100 ± 0.030/h (P = 0.04), respectively, asdetermined by using[U-13C]palmitate, andwere 0.278 ± 0.049 and 0.075 ± 0.013/h(P = 0.02), respectively, by using[1-13C]oleate. Weconclude that plasma free fatty acids are a source for intramusculartriglycerides and nonesterified fatty acids; the latter are likely thesynthetic precursors of the former. Uniformly and singly labeled[13C]fatty acidtracers will provide an important tool to study intramuscular fattyacid and triglyceride metabolism. 相似文献
7.
The biosynthetic pathway from D-glucose to L-(+)-tartaric acid(TA) in detached leaves of the bean, Phaseolus vulgaris L.,was studied in three cultivars, two of which were known to containTA and one of which lacked TA, with the aid of several putativeradiolabeled intermediates, namely D-[l-14C]glucose, D-[6-14C]glucose,D-[U-14C]glucose, D-[U-14C]gluconate, L-[U-14C]-ascorbic acid,L-[l-l4C]idonate, D-xylo-5-[U-14C]hexulosonate, D-xylo-5-[l-14C]hexulosonate,D-xylo-5-[6-l4C]hexulosonate and L-[U-l4C]threonate. D-[U-14C]Glucoseand D-[U-l4C]gluconate were converted to TA with low isotopicyield but this yield was further reduced when leaf tissues weresupplied with unlabeled D-gluconate or D-xylo-5-hexulosonate.D-xylo-5-[U-14C]Hexulosonate and D-xylo-5-[l-14C]hexulosonatewere good precursors of TA. D-xylo-5-[6-14C]Hexulosonate didnot furnish 14C to TA. Addition of a metabolic product of D-xylo-5-hexulosonate(which was labeled by D-xylo-5-[l-14C]hexulosonate but not byD-xylo-5-[6-14C]hexulosonate) to leaves labeled with D-xylo-5-[l-14C]hexulosonatedoubled the incorporation of 14C into TA. L-[U-14C]Ascorbicacid, L-[l-14C]idonate and L-[U-14C]threonate failed to producelabeled TA. A metabolic scheme to accommodate these observationsis presented. (Received October 21, 1988; Accepted March 29, 1989) 相似文献
8.
GROENEVELD H. W.; PETERS E. G. M.; KROESE G. W.; PAPENHUYZEN C. 《Annals of botany》1983,51(3):307-315
In 614-day-old etiolated seedlings of Euphorbia lashyrisa latex triterpene synthesis of 19 µg day1 wasrecorded. This production was proportional to stem growth. Laticiferdistribution in the cotyledons and stem was studied. In ultra-thinsections the occurrence of many mitochondria was observed. A14C-latex triterpene synthesis was measured after 14C-glucoseand 14C-sucrose uptake by the cotyledons in which most of the14C-triterpenes were synthesized. 14C-incorporation into theselipids from [114C]glucose, [6-14C]glucose and [3,414points to a glycolytic catabolism of glucose prior to terpenesynthesis. The possible involvement of mitochondria in thissynthesis is discussed. Euphorbia lathyris, triterpene synthesis, laticifer, latex, mitochondria, ultrastructure 相似文献
9.
10.
Bertocci Loren A.; Jones John G.; Malloy Craig R.; Victor Ronald G.; Thomas Gail D. 《Journal of applied physiology》1997,83(1):32-39
Bertocci, Loren A., John G. Jones, Craig R. Malloy, RonaldG. Victor, and Gail D. Thomas. Oxidation of lactateand acetate in rat skeletal muscle: analysis by13C-nuclear magnetic resonancespectroscopy. J. Appl. Physiol. 83(1): 32-39, 1997.The balance between carbohydrate and fatty acidutilization in skeletal muscle previously has been studied in vivo byusing a variety of methods such as arteriovenous concentrationdifferences and radioactive isotope tracer techniques. However, thesemethodologies provide only indirect estimates of substrate oxidation.We used 13C-nuclear magneticresonance (NMR) spectroscopy and non-steady-state isotopomer analysisto directly quantify the relative oxidation of two competing exogenoussubstrates in rat skeletal muscles. We infused[1,2-13C]acetate and[3-13C]lactateintravenously in anesthetized rats during the final 30 min of 35 (n = 10) or 95 (n = 10) min of intense, unilateral, rhythmic hindlimb contractions.13C-NMR spectroscopy andisotopomer analysis were performed on extracts of gastrocnemius andsoleus muscles from both the contracting and contralateralresting hindlimbs. We found that1)[13C]lactate and[13C]acetate were taken up and oxidized by both restingand contracting skeletal muscles; and2) high-intensity musclecontractions altered the pattern of substrate utilization such that therelative oxidation of acetate decreased while that of lactate remainedunchanged or increased. Based on these findings, we propose that13C-NMR spectroscopy incombination with isotopomer analysis can be used to study the generaldynamics of substrate competition between carbohydrates and fats in ratskeletal muscle. 相似文献
11.
5-Keto-D-[1-14C]gluconic acid, the most effective precursorof L(+)tartaric acid among all labeled compounds which haveever been tested in grapes, was found to be a good precursorof L(+)tartaric acid in a species of Pelargonium. The synthesisof labeled L(+)tartaric acid from D-[1-14C]glucose in Pelargoniumwas remarkably depressed when a 0.5% solution of D-gluconateor 5-keto-D-gluconate was administered continuously to leavestogether with D-[1-14C]glucose. Our results provide strong evidence that D-[1-14C]glucose ismetabolized in Pelargonium to give labeled L(+)tartaric acidvia (probably D-gluconic acid and) 5-keto-D-gluconic acid withoutpassing through L-ascorbic acid. Labeled L-idonic acid was found in young leaves of Pelargoniumwhich had been labeled with L-[U-14C]ascorbic acid. The synthesisof the labeled L-idonic acid increased when a 0.1% solutionof L-threonate was administered continuously to leaves togetherwith L-[U-14C]ascorbic acid. Specifically labeled compounds, recognized as the members ofthe synthetic pathway for L(+)tartaric acid from L-ascorbicacid via L-idonic acid in grapes, were administered to youngleaves of Pelargonium. Each compound (2-keto-L-[U-14C]idonicacid, L-[U-14C]idonic acid, 5-keto-D-[1-14C]gluconic acid and5-keto-D-[6-14C]gluconic acid) was partly metabolized, as ingrapes. The metabolic pathway starting from L-ascorbic acidto L(+)tartaric acid via L-idonic acid, however, did not actuallycontribute to the synthesis of L(+)tartaric acid in Pelargoniumprobably because the activity of each metabolic step was muchlower than that observed in grapes. (Received May 28, 1984; Accepted July 30, 1984) 相似文献
12.
The Metabolism of Abscisic Acid 总被引:7,自引:2,他引:5
The light-catalysed isomerization of (+)-abscisic acid (ABA)to its trans isomer during isolation from leaves was monitoredby the addition of (±)-[2-14C]ABA to the extraction medium.(+)Trans-abscisic acid (t-ABA) was found to occur naturallyin rose (Rosa arvensis) leaves at 20µg/kg fresh weight;(+)-ABA was present at 594µg/kg. (±)-[2-14D]Trans-abscisicacid was not isomerized enzymically to ABA in tomato shoots. (±)-Abscisic acid was converted by tomato shoots to awater-soluble neutral product, Metabolite B, whichwas identified as abscisyl-ß-D-glucopyranoside. When(±)-[2-14C]trans-abscisic acid in an equimolar mixturewith (±)-[2-14C}ABA was fed to tomato shoots it was convertedto its glucose ester 10 times faster than was ABA. Trans-abscisyl-ß-D-glucopyrano8ide only was formedfrom (±)-[2-14C]t-ABA in experiments lasting up to 30h. Glucosyl abscisate was formed slowly from ABA and the freeacid fraction contained an excess of the unnatural ().ABAas did the ABA released from abscisyl-ß-D-glucopyranosideby alkaline hydrolysis. The (+).ABA appeared to be the solesource of the acidic Metabolite C" previously noted. The concentrations of endogenous (+)-, (+)-[2-14C]-, and ()-[2-14C]ABAremaining as free acid, and also in the hydrolysate of abscisyl-ß-D-glucopyranoside,were measured by the ORD, UV absorption, and scintillation spectrometryof highly purified extracts of ABA from tomato shoots whichhad been supplied with racemic [2-l4C]ABA. 相似文献
13.
Microdialysis ethanol removal reflects probe recovery rather than local blood flow in skeletal muscle 总被引:2,自引:0,他引:2
Radegran G.; Pilegaard H.; Nielsen J. J.; Bangsbo J. 《Journal of applied physiology》1998,85(2):751-757
The present study compared the microdialysis ethanoloutflow-inflow technique for estimating blood flow (BF) in skeletalmuscle of humans with measurements by Doppler ultrasound of femoralartery inflow to the limb(BFFA). The microdialysis probeswere inserted in the vastus lateralis muscle and perfused with a Ringeracetate solution containing ethanol,[2-3H]adenosine (Ado),andD-[14C(U)]glucose.BFFA at rest increased from0.16 ± 0.02 to 1.80 ± 0.26 and 4.86 ± 0.53 l/minwith femoral artery infusion of Ado (AdoFA,i) at 125 and 1,000 µg · min1 · l1thigh volume (low dose and high dose, respectively;P < 0.05) and to 3.79 ± 0.37 and6.13 ± 0.65 l/min during one-legged, dynamic, thigh muscle exercisewithout and with high AdoFA,i,respectively (P < 0.05). The ethanoloutflow-to-inflow ratio (38.3 ± 2.3%) and the probe recoveries(PR) for [2-3H]Ado(35.4 ± 1.6%) and forD-[14C(U)]glucose(15.9 ± 1.1%) did not change withAdoFA,i at rest (P = not significant). During exercisewithout and with AdoFA,i, theethanol outflow-to-inflow ratio decreased(P < 0.05) to a similar level of17.5 ± 3.4 and 20.6 ± 3.2%, respectively(P = not significant), respectively,while the PR increased (P < 0.05) toa similar level (P = not significant)of 55.8 ± 2.8 and 61.2 ± 2.5% for[2-3H]Ado and to 42.8 ± 3.9 and 45.2 ± 5.1% forD-[14C(U)]glucose.Whereas the ethanol outflow-to-inflow ratio and PR correlated inverselyand positively, respectively, to the changes in BF during muscularcontractions, neither of the ratio nor PR correlated tothe AdoFA,i-induced BF increase.Thus the ethanol outflow-to-inflow ratio does not represent skeletalmuscle BF but rather contraction-induced changes in molecular transport in the interstitium or over the microdialysis membrane. 相似文献
14.
BECCARI E.; D'AGNOLO G.; MORPURGO G.; POCCHIARI F. 《Journal of experimental botany》1969,20(1):110-112
In Daucus carota cells cultivated in vitro, the ammonium ionstimulates the incorporation of radioactivity from labelledglucose and labelled pyruvate into CO2 and into the residueinsoluble in 60 per cent (v/v) ethanol. There is a higher 14CO2production from [6-14C2] glucose than from [6-14C] glucose.These results suggest a possible stimulation of glycolysis bythe ammonium ion. 相似文献
15.
Prior eccentric contractions impair maximal insulin action on muscle glucose uptake in the conscious rat 总被引:1,自引:0,他引:1
Asp Sven; Watkinson Allan; Oakes Nicholas D.; Kraegen Edward W. 《Journal of applied physiology》1997,82(4):1327-1332
Asp, Sven, Allan Watkinson, Nicholas D. Oakes, and Edward W. Kraegen. Prior eccentric contractions impair maximal insulin action on muscle glucose uptake in the conscious rat.J. Appl. Physiol. 82(4):1327-1332, 1997.Our aim was to examine the effect of prioreccentric contractions on insulin action locally in muscle in theintact conscious rat. Anesthetized rats performed one-leg eccentriccontractions through the use of calf muscle electrical stimulationfollowed by stretch of the active muscles. Two days later, basal andeuglycemic clamp studies were conducted with the rats in the awakefasted state. Muscle glucose metabolism was estimated from2-[14C(U)]deoxy-D-glucoseandD-[3-3H]glucose administration, and comparisons were made between the eccentrically stimulated and nonstimulated (control) calfmuscles. At midphysiological insulin levels, effects ofprior eccentric exercise on muscle glucose uptake were notstatistically significant. Maximal insulin stimulation revealed reducedincremental glucose uptake above basal(P < 0.05 in the red gastrocnemius;P < 0.1 in the white gastrocnemiusand soleus) and impaired net glycogen synthesis in all eccentricallystimulated muscles (P < 0.05). Weconclude that prior eccentric contractions impair maximal insulin action (responsiveness) on local muscle glucose uptake and glycogen synthesis in the conscious rat. 相似文献
16.
The R- and S-enantiomers of racemic [2-14C]Me 1', 4'-cis-diolof abscisic acid have been separated by high performance liquidchromatography on an optically-active Pirkle column. R-[2-14C]-and S-[2-14C]abscisic acids, formed from the Me 1', 4'-cis-diolby oxidation and alkyline hydrolysis were fed to tomato shootsand the extracts analysed by reversed phase high performanceliquid chromatography. R-[2-14C]abscisic acid formed mainlythe abscisic acid glucose ester (ABAGE), abscisic acid l'-glucoside(ABAGS) and an uncharacterized conjugate. Dihydrophaseic acid4'-B-D-glucoside, the major metabolite of RS-abscisic acid intomato shoots, was found to be derived virtually exclusivelyfrom the natural, S-abscisic acid. Phaseic acid and conjugatesof abscisic acid were also found as products of the naturallyoccurring enantiomer. The resolution method was used to measurethe relative proportions of R and S enantiomers in the freeacid liberated from conjugates formed from RS-[2-14C]ABA fedto shoots. The ratios show an excess of the R-enantiomer: 5.8:1, ABAGE; 29.4: 1, ABAGE; 8.3: 1 for an uncharacterized conjugateand 6.1: 1 for the residual free [2-14C]ABA. Key words: ABA, HPLC, Tomato 相似文献
17.
The metabolism of [2-14C]thymine, [2-14C]thymidine, [2-14C]uraciland [14C]uridine was investigated in protoplasts obtained fromsuspension cultures of Catharanthus roseus. Most of the exogenouslysupplied thymine, thymidine and uracil was degraded, and salvageof these pyrimidines accounted for 536 per cent of thetotal amount of 14C-labelled precursors which was metabolized.However, more than 80 per cent of the labelled uridine was utilizedfor the biosynthesis of nucleotides and nucleic acids, and therest was degraded. In contrast to the results from protoplastsof sugar cane cells in suspension culture, the data indicatethat protoplasts possess a pathway for the degradation of pyrimidines,and that the overall metabolism of these pyrimidines in protoplastsis very similar to the metabolism in the intact cells. Catharanthus roseus, madagascar periwinkle, protoplasts, pyrimidine metabolism 相似文献
18.
《Journal of experimental botany》1968,19(2):219
Page 678, line 3, for [4-14C] read [I-14C] Page 678, line 4, for [I-14C] read [4-14C] Page 679, line 17, for C-I of malate read C-4 of malate Page 679, line 18, for C-4 of malate read C-I of malate 相似文献
19.
Increased GLUT-4 translocation mediates enhanced insulin sensitivity of muscle glucose transport after exercise 总被引:5,自引:0,他引:5
Hansen Polly A.; Nolte Lorraine A.; Chen May M.; Holloszy John O. 《Journal of applied physiology》1998,85(4):1218-1222
The purpose of this study was to determinewhether the increase in insulin sensitivity of skeletal muscle glucosetransport induced by a single bout of exercise is mediated by enhancedtranslocation of the GLUT-4 glucose transporter to the cell surface.The rate of3-O-[3H]methyl-D-glucosetransport stimulated by a submaximally effective concentration ofinsulin (30 µU/ml) was approximately twofold greater in the musclesstudied 3.5 h after exercise than in those of the sedentary controls(0.89 ± 0.10 vs. 0.43 ± 0.05 µmol · ml1 · 10 min1; means ± SE forn = 6/group). GLUT-4 translocation wasassessed by using theATB-[2-3H]BMPAexofacial photolabeling technique. Prior exercise resulted in greatercell surface GLUT-4 labeling in response to submaximal insulintreatment (5.36 ± 0.45 dpm × 103/g in exercised vs. 3.00 ± 0.38 dpm × 103/g insedentary group; n = 10/group) thatclosely mirrored the increase in glucose transport activity. The signalgenerated by the insulin receptor, as reflected in the extent ofinsulin receptor substrate-1 tyrosine phosphorylation, was unchangedafter the exercise. We conclude that the increase in muscle insulinsensitivity of glucose transport after exercise is due to translocationof more GLUT-4 to the cell surface and that this effect is not due topotentiation of insulin-stimulated tyrosine phosphorylation. 相似文献
20.
Bryce, J. H. and ap Rees, T. 1985. Comparison of the respiratorymetabolism of Plantago lanceolata L. and Plantago major L.J.exp. Bot. 36 15591565. The aim of this work was to discover if the respiratory metabolismof the roots of Plantago lanceolata L. differed from that ofthe roots of Plantago major L. Measurements of oxygen uptakeand dry weight of excised root systems during growth of seedlingsprovided evidence that the two species differed in the amountof respiration needed to support a given increase in dry weight.Excised root systems were given a 6-h pulse in [U-14C]sucrosefollowed by a 16.5-h chase in sucrose. The detailed distributionof 14C amongst the major components of the roots at the endof the pulse and the chase revealed no significant differencebetween the two species. Patterns of 14CO2 production from [1-14C],[2-14C], [3,4-14C], and [6-14C]glucose of excised root systemsfrom plants of three ages were similar for the two species.It is suggested that there is no conclusive evidence for anysignificant inherent difference in the respiratory metabolismof the roots of the two species. Key words: 14C sugar metabolism, respiration, roots, Plantago 相似文献