Stimulation of glucose transport in skeletal muscle by hypoxia

Hypoxia caused a progressive cytochalasin B-inhibitable increase in the rate of 3-O-methylglucose transport in rat epitrochlearis muscles to a level approximately six-fold above basal. Muscle ATP concentration was well maintained during hypoxia, and increased glucose transport activity was still present after 15 min of reoxygenation despite repletion of phosphocreatine. However, the increase in glucose transport activity completely reversed during a 180-min-long recovery in oxygenated medium. In perfused rat hindlimb muscles, hypoxia caused an increase in glucose transporters in the plasma membrane, suggesting that glucose transporter translocation plays a role in the stimulation of glucose transport by hypoxia. The maximal effects of hypoxia and insulin on glucose transport activity were additive, whereas the effects of exercise and hypoxia were not, providing evidence suggesting that hypoxia and exercise stimulate glucose transport by the same mechanism. Caffeine, at a concentration too low to cause muscle contraction or an increase in glucose transport by itself, markedly potentiated the effect of a submaximal hypoxic stimulus on sugar transport. Dantrolene significantly inhibited the hypoxia-induced increase in 3-O-methylglucose transport. These effects of caffeine and dantrolene suggest that Ca2+ plays a role in the stimulation of glucose transport by hypoxia.

Download Full-text

Qualitative and quantitative comparison of glucose transport activity and glucose transporter concentration in plasma membranes from basal and insulin-stimulated rat adipose cells

Biochemical Journal ◽

10.1042/bj2490155 ◽

1988 ◽

Vol 249 (1) ◽

pp. 155-161 ◽

Cited By ~ 63

Author(s):

H G Joost ◽

T M Weber ◽

S W Cushman

Keyword(s):

Activation Energy ◽

Plasma Membrane ◽

Membrane Transport ◽

Glucose Transport ◽

Plasma Membranes ◽

Glucose Transporter ◽

Cytochalasin B ◽

Transport Activity ◽

Adipose Cells ◽

Stimulation Of

Conditions are described which allow the isolation of rat adipose-cell plasma membranes retaining a large part of the stimulatory effect of insulin in intact cells. In these membranes, the magnitude of glucose-transport stimulation in response to insulin was compared with the concentration of transporters as measured with the cytochalasin-B-binding assay or by immunoblotting with an antiserum against the human erythrocyte glucose transporter. Further, the substrate- and temperature-dependencies of the basal and insulin-stimulated states were compared. Under carefully controlled homogenization conditions, insulin-treated adipose cells yielded plasma membranes with a glucose transport activity 10-15-fold higher than that in membranes from basal cells. Insulin increased the transport Vmax. (from 1,400 +/- 300 to 15,300 +/- 3,400 pmol/s per mg of protein; means +/- S.E.M.; assayed at 22 degrees C) without any significant change in Km (from 17.8 +/- 4.4 to 18.9 +/- 1.4 nM). Arrhenius plots of plasma-membrane transport exhibited a break at 21 degrees C, with a higher activation energy over the lower temperature range. The activation energy over the higher temperature range was significantly lower in membranes from basal than from insulin-stimulated cells [27.7 +/- 5.0 kJ/mol (6.6 +/- 1.2 kcal/mol) and 45.3 +/- 2.1 kJ/mol (10.8 +/- 0.5 kcal/mol) respectively], giving rise to a larger relative response to insulin when transport was assayed at 37 degrees C as compared with 22 degrees C. The stimulation of transport activity at 22 degrees C was fully accounted for by an increase in the concentration of transporters measured by cytochalasin B binding, if a 5% contamination of plasma membranes with low-density microsomes was assumed. However, this 10-fold stimulation of transport activity contrasted with an only 2-fold increase in transporter immunoreactivity in membranes from insulin-stimulated cells. These data suggest that, in addition to stimulating the translocation of glucose transporters to the plasma membrane, insulin appears to induce a structural or conformational change in the transporter, manifested in an altered activation energy for plasma-membrane transport and possibly in an altered immunoreactivity as assessed by Western blotting.

Download Full-text

Effects of phenylarsine oxide on stimulation of glucose transport in rat skeletal muscle

AJP Cell Physiology ◽

10.1152/ajpcell.1990.258.4.c648 ◽

1990 ◽

Vol 258 (4) ◽

pp. C648-C653 ◽

Cited By ~ 32

Author(s):

E. J. Henriksen ◽

J. O. Holloszy

Keyword(s):

Skeletal Muscle ◽

Glucose Transport ◽

Cytochalasin B ◽

Contractile Activity ◽

Transport Activity ◽

Rat Skeletal Muscle ◽

Phenylarsine Oxide ◽

Muscle Glucose Transport ◽

Glucose Analogue ◽

Stimulation Of

The trivalent arsenical phenylarsine oxide (PAO) inhibits insulin-stimulated glucose transport in adipocytes and skeletal muscle through direct interactions with vicinal sulfhydryls. In muscle, glucose transport is also activated by contractile activity and hypoxia. It was therefore the purpose of the present study to investigate whether vicinal sulfhydryls are involved in the stimulation of glucose transport activity in the isolated rat epitrochlearis muscle by hypoxia or contractions. PAO (greater than 5 microM) caused a twofold increase in rate of transport of the nonmetabolizable glucose analogue 3-O-methylglucose (3-MG) that was completely prevented by cytochalasin B, the vicinal dithiol dimercaptopropanol, dantrolene, or 9-aminoacridine, both inhibitors of sarcoplasmic reticulum Ca2+ release, or omission of extracellular Ca2+. Although PAO treatment (greater than or equal to 20 microM) prevented approximately 80% of the increase in 3-MG transport caused by insulin, it resulted in only a approximately 50% inhibition of the stimulation of 3-MG transport by either hypoxia or contractile activity. PAO treatment (40 microM) of muscles already maximally stimulated by insulin, contractile activity, or hypoxia did not reverse the enhanced rate of 3-MG transport. These data suggest that vicinal sulfhydryls play a greater role in the activation of glucose transport by insulin than by muscle contractions or hypoxia. The finding that PAO inhibits the stimulation of glucose transport, but does not affect glucose transport after it has been stimulated, provides evidence that vicinal sulfhydryls are involved in the pathways for glucose transport activation in muscle, but not in the glucose transport mechanism itself.

Download Full-text

The effects of muscle contraction and insulin on glucose-transporter translocation in rat skeletal muscle

Biochemical Journal ◽

10.1042/bj2970539 ◽

1994 ◽

Vol 297 (3) ◽

pp. 539-545 ◽

Cited By ~ 48

Author(s):

J T Brozinick ◽

G J Etgen ◽

B B Yaspelkis ◽

J L Ivy

Keyword(s):

Skeletal Muscle ◽

Plasma Membrane ◽

Muscle Contraction ◽

Glucose Uptake ◽

Protein Concentration ◽

Glucose Transporter ◽

Cytochalasin B ◽

Protein Distribution ◽

Sprague Dawley ◽

Glut 4

The effect of electrically induced muscle contraction, insulin (10 m-units/ml) and electrically-induced muscle contraction in the presence of insulin on insulin-regulatable glucose-transporter (GLUT-4) protein distribution was studied in female Sprague-Dawley rats during hindlimb perfusion. Plasma-membrane cytochalasin B binding increased approximately 2-fold, whereas GLUT-4 protein concentration increased approximately 1.5-fold above control with contractions, insulin, or insulin + contraction. Microsomal-membrane cytochalasin B binding and GLUT-4 protein concentration decreased by approx. 30% with insulin or insulin + contraction, but did not significantly decrease with contraction alone. The rate of muscle glucose uptake was assessed by determining the rate of 2-deoxy[3H]glucose accumulation in the soleus, plantaris, and red and white portions of the gastrocnemius. Both contraction and insulin increased glucose uptake significantly and to the same degree in the muscles examined. Insulin + contraction increased glucose uptake above that of insulin or contraction alone, but this effect was only statistically significant in the soleus, plantaris and white gastrocnemius. The combined effects of insulin + contraction of glucose uptake were not fully additive in any of the muscles investigated. These results suggest that (1) insulin and muscle contraction are mobilizing two separate pools of GLUT-4 protein, and (2) the increase in skeletal-muscle glucose uptake due to insulin + contraction is not due to an increase in plasma-membrane GLUT-4 protein concentration above that observed for insulin or contraction alone.

Download Full-text

Calcium stimulates glucose transport in skeletal muscle by a pathway independent of contraction

AJP Cell Physiology ◽

10.1152/ajpcell.1991.260.3.c555 ◽

1991 ◽

Vol 260 (3) ◽

pp. C555-C561 ◽

Cited By ~ 123

Author(s):

J. H. Youn ◽

E. A. Gulve ◽

J. O. Holloszy

Keyword(s):

Skeletal Muscle ◽

Glucose Transport ◽

Cytochalasin B ◽

Muscle Tension ◽

Creatine Phosphate ◽

Transport Activity ◽

Dose Dependent Increase ◽

Dose Dependent ◽

Glucose Analogue ◽

Stimulation Of

In this study we investigated the possibility that an increase in cytoplasmic Ca2+ concentration that is too low to cause muscle contraction can induce an increase in glucose transport activity in skeletal muscle. The compound N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), which induces Ca2+ release from the sarcoplasmic reticulum (SR), caused a dose-dependent increase in tension in rat epitrochlearis muscles at concentrations more than approximately 200 microM. Although 100 microM W-7 did not increase muscle tension, it accelerated loss of preloaded 45Ca2+. Glucose transport activity, measured with the nonmetabolizable glucose analogue 3-O-methylglucose, increased sixfold in muscles treated for 100 min with 50 microM W-7 (P less than 0.001) and eightfold in response to 100 microM W-7 (P less than 0.001). The increase in glucose transport activity was completely blocked with 25 microM cytochalasin B. There was no decrease in ATP or creatine phosphate concentrations ([approximately P]) in muscles incubated with 50 microM W-7. Dantrolene (25 microM), which blocks Ca2+ release from the SR, blocked the effects of W-7 both on 45Ca2+ release and on glucose transport activity. 9-Aminoacridine, another inhibitor of Ca2+ release from the SR, also blocked the stimulation of hexose transport by W-7. Caffeine, a compound structurally unrelated to W-7 that also releases Ca2+ from the SR, also increased glucose transport activity. Incubation of muscles with 3 mM caffeine for 30 min, which did not cause contraction or lower [approximately P], induced a threefold increase in 3-O-methylglucose transport (P less than 0.001). These results provide evidence suggesting that an increase in cytoplasmic Ca2+ too low to cause contraction or [approximately P] depletion can bring about an increase in glucose transport activity in skeletal muscle.

Download Full-text

Characterization of human glucose transporter (GLUT) 11 (encoded by SLC2A11), a novel sugar-transport facilitator specifically expressed in heart and skeletal muscle

Biochemical Journal ◽

10.1042/bj3590443 ◽

2001 ◽

Vol 359 (2) ◽

pp. 443-449 ◽

Cited By ~ 48

Author(s):

Holger DOEGE ◽

Andreas BOCIANSKI ◽

Andrea SCHEEPERS ◽

Hubertus AXER ◽

Jürgen ECKEL ◽

...

Keyword(s):

Skeletal Muscle ◽

Amino Acid ◽

Glucose Transport ◽

Glucose Transporter ◽

Specific Binding ◽

Sequence Similarity ◽

Sugar Transport ◽

Amino Acid Identity ◽

Sugar Transporter ◽

Transport Activity

Human GLUT11 (encoded by the solute carrier 2A11 gene, SLC2A11) is a novel sugar transporter which exhibits significant sequence similarity with the members of the GLUT family. The amino acid sequence deduced from its cDNAs predicts 12 putative membrane-spanning helices and all the motifs (sugar-transporter signatures) that have previously been shown to be essential for sugar-transport activity. The closest relative of GLUT11 is the fructose transporter GLUT5 (sharing 41.7% amino acid identity with GLUT11). The human GLUT11 gene (SLC2A11) consists of 12 exons and is located on chromosome 22q11.2. In human tissues, a 7.2kb transcript of GLUT11 was detected exclusively in heart and skeletal muscle. Transfection of COS-7 cells with GLUT11 cDNA significantly increased the glucose-transport activity reconstituted from membrane extracts as well as the specific binding of the sugar-transporter ligand cytochalasin B. In contrast to that of GLUT4, the glucose-transport activity of GLUT11 was markedly inhibited by fructose. It is concluded that GLUT11 is a novel, muscle-specific transport facilitator that is a member of the extended GLUT family of sugar/polyol-transport facilitators.

Download Full-text

Glucose transport and GLUT4 protein distribution in skeletal muscle of GLUT4 transgenic mice

Biochemical Journal ◽

10.1042/bj3130133 ◽

1996 ◽

Vol 313 (1) ◽

pp. 133-140 ◽

Cited By ~ 28

Author(s):

Joseph T. BROZINICK ◽

Benedict B. YASPELKIS ◽

Cindy M. WILSON ◽

Kristen E. GRANT ◽

E. Michael GIBBS ◽

...

Keyword(s):

Skeletal Muscle ◽

Plasma Membrane ◽

Glucose Metabolism ◽

Glucose Transport ◽

Protein Concentration ◽

Glucose Transporter ◽

Protein Distribution ◽

Transport Activity ◽

Insulin Stimulation ◽

Hind Limbs

The aim of the present investigation was to determine whether the subcellular distribution and insulin-stimulated translocation of the GLUT4 isoform of the glucose transporter are affected when GLUT4 is overexpressed in mouse skeletal muscle, and if the overexpression of GLUT4 alters maximal insulin-stimulated glucose transport and metabolism. Rates of glucose transport and metabolism were assessed by hind-limb perfusion in GLUT4 transgenic (TG) mice and non-transgenic (NTG) controls. Glucose-transport activity was determined under basal (no insulin), submaximal (0.2 m-unit/ml) and maximal (10 m-units/ ml) insulin conditions using a perfusate containing 8 mM 3-O-methyl-D-glucose. Glucose metabolism was quantified by perfusing the hind limbs for 25 min with a perfusate containing 8 mM glucose and 10 m-units/ml insulin. Under basal conditions, there was no difference in muscle glucose transport between TG (1.10±0.10 μmol/h per g; mean±S.E.M.) and NTG (0.93±0.16 μmol/h per g) mice. However, TG mice displayed significantly greater glucose-transport activity during submaximal (4.42±0.49 compared with 2.69±0.33 μmol/h per g) and maximal (11.68±1.13 compared with 7.53±0.80 μmol/h per g) insulin stimulation. Nevertheless, overexpression of the GLUT4 protein did not alter maximal rates of glucose metabolism. Membrane purification revealed that, under basal conditions, plasma-membrane (~ 12-fold) and intracellular-membrane (~ 4-fold) GLUT4 protein concentrations were greater in TG than NTG mice. Submaximal insulin stimulation did not increase plasma-membrane GLUT4 protein concentration whereas maximal insulin stimulation increased this protein in both NTG (4.1-fold) and TG (2.6-fold) mice. These results suggest that the increase in insulin-stimulated glucose transport following overexpression of the GLUT4 protein is limited by factors other than the plasma-membrane GLUT4 protein concentration. Furthermore, GLUT4 overexpression is not coupled to glucose-metabolic capacity.

Download Full-text

Regulation of cell surface GLUT4 in skeletal muscle of transgenic mice

Biochemical Journal ◽

10.1042/bj3210075 ◽

1997 ◽

Vol 321 (1) ◽

pp. 75-81 ◽

Cited By ~ 17

Author(s):

Joseph T. BROZINICK ◽

Scott C. McCOID ◽

Thomas H. REYNOLDS ◽

Cindy M. WILSON ◽

Ralph W. STEVENSON ◽

...

Keyword(s):

Skeletal Muscle ◽

Cell Surface ◽

Glucose Transport ◽

Glucose Transporter ◽

Subcellular Fractionation ◽

Muscle Membrane ◽

Transport Activity ◽

Hindlimb Muscles ◽

Subcellular Membrane ◽

Glucose Transporter Glut4

Marked overexpression of the glucose transporter GLUT4 in skeletal muscle membrane fractions of GLUT4 transgenic (TG) mice is accompanied by disproportionately small increases in basal and insulin-stimulated glucose transport activity. Thus we have assessed cell surface GLUT4 by photolabelling with the membrane-impermeant reagent 2-N-[4-(1-azi-2,2,2-trifluoroethyl)benzoyl]-1,3-bis(d-mannos-4-yloxy)-2-propylamine (ATB-BMPA) and measured the corresponding glucose transport activity using 2-deoxyglucose in isolated extensor digitorum longus (EDL) muscles from non-transgenic (NTG) and GLUT4 TG mice in the absence and presence of 13.3 nM (2000 µ-units/ml) insulin, without or with hypoxia as a model of muscle contraction. TG mice displayed elevated rates of glucose transport activity under basal and insulin-stimulated conditions, and in the presence of insulin plus hypoxia, compared with NTG mice. Photoaffinity labelling of cell surface GLUT4 indicated corresponding elevations in plasma membrane GLUT4 in the basal and insulin-stimulated states, and with insulin plus hypoxia, but no difference in cell surface GLUT4 during hypoxia stimulation. Subcellular fractionation of hindlimb muscles confirmed the previously observed 3-fold overexpression of GLUT4 in the TG compared with the NTG mice. These results suggest that: (1) alterations in glucose transport activity which occur with GLUT4 overexpression in EDL muscles are directly related to cell surface GLUT4 content, regardless of the levels observed in the corresponding subcellular membrane fractions, (2) while overexpression of GLUT4 influences both basal and insulin-stimulated glucose transport activity, the response to hypoxia/contraction-stimulated glucose transport is unchanged, and (3) subcellular fractionation provides little insight into the subcellular trafficking of GLUT4, and whatever relationship is demonstrated in EDL muscles from NTG mice is disrupted on GLUT4 overexpression.

Download Full-text

Glycaemia regulates the glucose transporter number in the plasma membrane of rat skeletal muscle

Biochemical Journal ◽

10.1042/bj2840341 ◽

1992 ◽

Vol 284 (2) ◽

pp. 341-348 ◽

Cited By ~ 45

Author(s):

D Dimitrakoudis ◽

T Ramlal ◽

S Rastogi ◽

M Vranic ◽

A Klip

Keyword(s):

Skeletal Muscle ◽

Plasma Membrane ◽

Glucose Transport ◽

Transport System ◽

Plasma Membranes ◽

Glucose Transporter ◽

Cytochalasin B ◽

Glucose Transporters ◽

Mrna Levels ◽

Rat Skeletal Muscle

The number of glucose transporters was measured in isolated membranes from diabetic-rat skeletal muscle to determine the role of circulating blood glucose levels in the control of glucose uptake into skeletal muscle. Three experimental groups of animals were investigated in the post-absorptive state: normoglycaemic/normoinsulinaemic, hyperglycaemic/normoinsulinaemic and hyperglycaemic/normoinsulinaemic made normoglycaemic/normoinsulinaemic by phlorizin treatment. Hyperglycaemia caused a reversible decrease in total transporter number, as measured by cytochalasin B binding, in both plasma membranes and internal membranes of skeletal muscle. Changes in GLUT4 glucose transporter protein mirrored changes in cytochalasin B binding in plasma membranes. However, there was no recovery of GLUT4 levels in intracellular membranes with correction of glycaemia. GLUT4 mRNA levels decreased with hyperglycaemia and recovered only partially with correction of glycaemia. Conversely, GLUT1 glucose transporters were only detectable in the plasma membranes; the levels of this protein varied directly with glycaemia, i.e. in the opposite direction to GLUT4 glucose transporters. This study demonstrates that hyperglycaemia, in the absence of hypoinsulinaemia, is capable of down-regulating the glucose transport system in skeletal muscle, the major site of peripheral resistance to insulin-stimulated glucose transport in diabetes. Furthermore, correction of hyperglycaemia causes a complete restoration of the transport system in the basal state (determined by the transporter number in the plasma membrane), but possibly only an incomplete recovery of the transport system's ability to respond to insulin (since there is no recovery of GLUT4 levels in the intracellular membrane insulin-responsive transporter pool). Finally, the effect of hyperglycaemia is specific for glucose transporter isoforms, with GLUT1 and GLUT4 proteins varying respectively in parallel and opposite directions to levels of glycaemia.

Download Full-text

Expression and cellular localization of glucose transporters (GLUT1, GLUT3, GLUT4) during differentiation of myogenic cells isolated from rat foetuses

Journal of Cell Science ◽

10.1242/jcs.107.3.487 ◽

1994 ◽

Vol 107 (3) ◽

pp. 487-496 ◽

Cited By ~ 3

Author(s):

I. Guillet-Deniau ◽

A. Leturque ◽

J. Girard

Keyword(s):

Skeletal Muscle ◽

Plasma Membrane ◽

Glucose Transport ◽

Cell Fusion ◽

Cellular Localization ◽

Glucose Transporter ◽

Glucose Transporters ◽

Short Exposure ◽

Myoblast Differentiation ◽

Igf I

Skeletal muscle regeneration is mediated by the proliferation of myoblasts from stem cells located beneath the basal lamina of myofibres, the muscle satellite cells. They are functionally indistinguishable from embryonic myoblasts. The myogenic process includes the fusion of myoblasts into multinucleated myotubes, the biosynthesis of proteins specific for skeletal muscle and proteins that regulates glucose metabolism, the glucose transporters. We find that three isoforms of glucose transporter are expressed during foetal myoblast differentiation: GLUT1, GLUT3 and GLUT4; their relative expression being dependent upon the stage of differentiation of the cells. GLUT1 mRNA and protein were abundant only in myoblasts from 19-day-old rat foetuses or from adult muscles. GLUT3 mRNA and protein, detectable in both cell types, increased markedly during cell fusion, but decreased in contracting myotubes. GLUT4 mRNA and protein were not expressed in myoblasts. They appeared only in spontaneously contracting myotubes cultured on an extracellular matrix. Insulin or IGF-I had no effect on the expression of the three glucose transporter isoforms, even in the absence of glucose. The rate of glucose transport, assessed using 2-[3H]deoxyglucose, was 2-fold higher in myotubes than in myoblasts. Glucose deprivation increased the basal rate of glucose transport by 2-fold in myoblasts, and 4-fold in myotubes. The cellular localization of the glucose transporters was directly examined by immunofluorescence staining. GLUT1 was located on the plasma membrane of myoblasts and myotubes. GLUT3 was located intracellularly in myoblasts and appeared also on the plasma membrane in myotubes. Insulin or IGF-I were unable to target GLUT3 to the plasma membrane. GLUT4, the insulin-regulatable glucose transporter isoform, appeared only in contracting myotubes in small intracellular vesicles. It was translocated to the plasma membrane after a short exposure to insulin, as it is in skeletal muscle in vivo. These results show that there is a switch in glucose transporter isoform expression during myogenic differentiation, dependent upon the energy required by the different stages of the process. GLUT3 seemed to play a role during cell fusion, and could be a marker for the muscle's ability to regenerate.

Download Full-text

Kinetics of glucose transport in rat skeletal muscle membrane vesicles: effects of insulin and contractions

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1992.262.5.e700 ◽

1992 ◽

Vol 262 (5) ◽

pp. E700-E711 ◽

Cited By ~ 11

Author(s):

T. Ploug ◽

H. Galbo ◽

T. Ohkuwa ◽

J. Tranum-Jensen ◽

J. Vinten

Keyword(s):

Skeletal Muscle ◽

Plasma Membrane ◽

Glucose Transport ◽

Cytochalasin B ◽

Equilibrium Distribution ◽

Initial Rate ◽

Membrane Vesicles ◽

Membrane Preparation ◽

Muscle Membrane ◽

Distribution Space

To study the mechanism of acceleration of glucose transport in skeletal muscle after stimulation with insulin and contractions, we isolated a subcellular vesicular membrane fraction, highly enriched in the plasma membrane enzyme K(+)-stimulated p-nitrophenylphosphatase and also enriched in some intracellular membranes. Protein recovery, morphology, lipid content, marker enzyme activities, total intravesicular volume, Western blot quantitation of GLUT-1, and glucose-inhibitable cytochalasin B binding were identical in membrane fractions from control, insulin-stimulated, contraction-stimulated, and insulin- and contraction-stimulated muscle. Time course of D-[3H]glucose entry in membrane vesicles at equilibrium exchange conditions showed that initial rate of transport at 30 mM of glucose was increased 19-fold and that equilibrium distribution space was increased 4-fold in vesicles from maximum stimulated muscle. The effects of insulin and contractions on initial rate of transport as well as on equilibrium distribution space were additive, and stimulation increased the substrate saturability of glucose transport. Furthermore, cytochalasin B binding to membranes prepared by using less centrifugation time than usual showed that, after stimulation with insulin and contractions, at least 35% of the total number of glucose transporters were redistributed from one kind of vesicles to a more slowly sedimenting kind of vesicles, probably reflecting translocation within the membrane preparation from intracellular vesicles to the plasma membrane upon stimulation. In the present membrane preparation the effects of insulin and/or contractions on glucose transport resemble those seen in intact muscle, and the effects are thus not dependent on cellular integrity.(ABSTRACT TRUNCATED AT 250 WORDS)

Download Full-text