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  • 1
    Electronic Resource
    Electronic Resource
    Lactate transport by skeletal muscle sarcolemmal vesicles (1993)
    Springer
    Molecular and cellular biochemistry 122 (1993), S. 113-121 
    Details
    ISSN: 1573-4919
    Keywords: membrane transport ; sarcolemmal vesicles ; lactate ; inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Recent studies have indicated that lactate traversal of the sarcolemmal membrane of skeletal muscle could be a carrier mediated process. In the present study, the initial rates of L(+)-lactate flux (Jlact) were measured in highly purified rat hindlimb skeletal muscle sarcolemmal vesicles. Fluxes were determined by the vesicle uptake of L(+)-[U-14C] lactate from the extra-vesicular medium. Jlact was saturable with respect to increasing concentrations of L(+)-lactate. Regression of these data to the Michaelis-Menten equation yielded a Km of 12.5 mM. Jlact was inhibited 81% by 10 mM pyruvate and 83% by 5mM alpha-cyano 4 hydroxycinnamate (p〈0.05), but not by D-lactate indicating the presence of a stereoselective monocarboxylate transporter in the sarcolemmal membrane. Preincubation of the vesicles with the protein modifier, N-ethylmaleimide (20mM), inhibited Jlact by 86% (p〈0.05). An inhibitor of the inorganic anion exchanger, SITS (1mM), had no effect on Jlact. However, Jlact was markedly sensitive to an inwardly directed proton gradient (p〈0.05), and the flux was more closely related to the concentration of external ionic L(+)-lactate than to the protonated (HLa) form. These studies suggest that skeletal muscle sarcolemmal membranes possess a specific transport system for L-lactate and other monocarboxylates, which has similar properties to the lactate carrier described for several other tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01076095
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  • 2
    Electronic Resource
    Electronic Resource
    Chronic muscle stimulation increases lactate transport in rat skeletal muscle (1996)
    Springer
    Molecular and cellular biochemistry 156 (1996), S. 51-57 
    Details
    ISSN: 1573-4919
    Keywords: electrical stimulation ; giant sarcolemmal vesicles ; muscle activity ; training
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The aim of this study was to examine the effects of chronic low frequency stimulation on the lactate transport across the plasma membrane of the tibialis anterior (TA) muscle of the rat. Stimulating electrodes were implanted on either side of the peroneal nerve in one hindlimb. Chronic stimulation (10 Hz, 50 psec bursts, 24 h/day) commenced 7 days after surgery, and were continued for 7 days. Animals were then left for 24 h, and thereafter muscles were obtained. Cytochrome C-oxidase activity was increased 1.9-fold in the stimulated TA compared to the control TA (p 〈 0.05). Lactate transport (zero-trans) was measured in giant sarcolemmal vesicles obtained from the chronically stimulated TA and the control TA. At each of the concentrations used in these studies a significant increase in lactate transport was observed: 2.8-fold increase at 1 mM lactate p 〈 0.05); 2-fold increases at both 30 mM and 50 mM lactate p 〈 0.05). These studies have shown that lactate transport capacity is markedly increased in response to chronic muscle contraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239319
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  • 3
    Electronic Resource
    Electronic Resource
    Muscle palmitate uptake and binding are saturable and inhibited by antibodies to FABPPM (2000)
    Springer
    Molecular and cellular biochemistry 210 (2000), S. 53-63 
    Details
    ISSN: 1573-4919
    Keywords: free fatty acids ; skeletal muscle ; fatty acid-binding protein ; FFA transport ; FFA metabolism ; fiber type
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Studies show that uptake of long-chain fatty acids (LCFA) across the plasma membranes (PM) may occur partly via a carrier-mediated process and that the plasma membrane fatty acid-binding protein (FABPPM) may be a component of this system. To test the hypothesis that FABPPM is involved in transsarcolemmal transport of LCFA in muscle, we measured palmitate uptake in giant sarcolemmal vesicles and palmitate binding to PM proteins in rat muscles, (1) in the presence of increasing amounts of unbound palmitate and (2) in the absence or presence of antibody to FABPPM. Both palmitate uptake and binding were found to be saturable functions of the unbound palmitate concentration with calculated Vmax values of 10.5 ± 1.2 pmol/mg protein/15 sec and 45.6 ± 2.9 nmol/mg protein/15 min and Km values of 12.8 ± 3.8 and 18.4 ± 1.8 nmol/L, respectively. The Vmax values for both palmitate uptake and binding were significantly decreased by 75-79% in the presence of a polyclonal antibody to the rat hepatic FABPPM. Antibody inhibition was found to be dose-dependent and specific to LCFA. Glucose uptake was not affected by the presence of the antibody to FABPPM. Palmitate uptake and binding were also inhibited in the presence of trypsin and phloretin. These results support the hypothesis that transsarcolemmal LCFA transport occurs in part by a carrier-mediated process and that FABPPM is a component of this process in muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007046929776
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  • 4
    Electronic Resource
    Electronic Resource
    Palmitate incorporation into lipids pools of contracting red and white muscles (1997)
    Springer
    Molecular and cellular biochemistry 166 (1997), S. 73-83 
    Details
    ISSN: 1573-4919
    Keywords: palmitic acid ; phospholipids ; mono-acylglycerols ; di-acylglycerols ; tri-acylglycerols ; free fatty acids ; cholesterol ; cholesterol esters ; sphingomyelin ; phosphatidylcholine ; phosphatidylserine ; phosphatidylinositol ; phosphatidylethanolamine ; cardiolipin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We compared the incorporation of the blood-borne [14C]-palmitate into selected lipid and phospholipid pools in rat muscles (soleus, red and white gastrocnemius), at rest and during contractions (15 and 60 tetani/min) in one leg (5 min) while the contralateral leg served as a control. [1-14C]-palmitate (20 µCi/rat) was administered into the carotid artery (t = 1 min). [14C]-palmitate deposition was greatest in soleus (100%) and lower in red (82%) and white gastrocnemius muscles (63%), respectively (p 〈 0.05). [14C] was deposited primarily into the tri-acylglycerol (∼50%) and phospholipid pools (∼30%) of soleus and red gastrocnemius muscles, and into the di-acylglycerol (∼30%), tri-acylglycerol (∼30%) and phospholipid pools (∼30%) in white gastrocnemius muscle. During contraction the concentrations of tri-acylglycerol were not changed. But, contraction increased [14C]-palmitate incorporation into soleus and red gastrocnemius muscles (600-700%) and into white gastrocnemius muscles (200%). Slightly more [14C] was directed from the phospholipids into the tri-acylglycerol pool during contraction. [14C]-palmitate deposition was also increased in the subclasses of phospholipids during contraction in red and white gastrocnemius. In conclusion, the deposition of [14C]palmitate into different lipid and phospholipid pools is quite rapid, and is dependent on contraction and the muscle fiber type. (Mol Cell Biochem 166: 73-83, 1997)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006882515938
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  • 5
    Electronic Resource
    Electronic Resource
    Denervation provokes greater reductions in insulin-stimulated glucose transport in muscle than severe diabetes (2000)
    Springer
    Molecular and cellular biochemistry 210 (2000), S. 81-89 
    Details
    ISSN: 1573-4919
    Keywords: streptozotocin ; contraction ; GLUT-4 ; GLUT-4 mRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We have examined the independent and combined effects of insulin insufficiency (streptozotocin (STZ)-induced diabetes, 85 mg/kg i.p.) and reduced muscle activity (denervation) (7 days) on basal, insulin-stimulated and contraction-stimulated glucose transport in rat muscles (soleus, red and white gastrocnemius). There were four treatments: control, denervated, diabetic, and denervated + diabetic muscles. Contraction-stimulated glucose transport was lowered (~ 50%) (p 〈 0.05) to the same extent in all experimental groups. In contrast, there was a much smaller reduction insulin-stimulated glucose transport in muscles from diabetic animals (18-24% reduction, p 〈 0.05) than in denervated muscles (40-60% reduction, p 〈 0.05) and in denervated + diabetic muscles (40-60% reduction, p 〈 0.05). GLUT-4 mRNA reduction was greatest in denervated + diabetic muscles (~ -75%, p 〈 0.05). GLUT-4 protein was decreased (p 〈 0.05) to a similar extent in all three experimental conditions (~ -30-40%). In conclusion, (1) muscle inactivity (denervation) and STZ-induced diabetes had similar effects on reducing contraction-stimulated glucose transport, but (2) muscle inactivity (denervation), rather than severe diabetes, produced a 2-fold greater impairment in skeletal muscle insulin-stimulated glucose transport.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007108025929
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  • 6
    Electronic Resource
    Electronic Resource
    Dependence of lactate removal on muscle metabolism in man (1978)
    Springer
    European journal of applied physiology 39 (1978), S. 89-97 
    Details
    ISSN: 1439-6327
    Keywords: Recovery exercise ; Oxygen consumption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary If lactate is primarily oxidized in skeletal muscle in man, it is expected that lactate uptake would increase linearly with increasing muscle metabolism (VO2). Therefore, lactate removal was investigated (N=9) after 6 min exercise bouts (90% VO2 max), at rest, and during 30 min of recovery exercise, when the relative intensities were constant to equate lactate production while permitting exercise metabolism (VO2) to vary. Recovery exercises were therefore conducted at 26.8% VO2 max for arm exercise, 26.8% VO2 max for leg exercise, and 29% VO2 max for combined arm and leg exercise. These exercise intensities were calculated from VO2 max values established separately for each of the three modes of exercise. Lactate removal was slowest at rest (p〈0.05). Removal during leg recovery was faster than during the arm condition (p〈0.05), but the leg removal was not different from the combined arm and leg condition (p〉0.05). The VO2 cost of the arm (0.73±0.04 l/min), leg (1.04±0.05 l/min) and combined arm and leg exercise (1.23±0.10 l/min) were distinctly different from each other (p〈0.05). There was a high correlation (r=0.92) between VO2 cost, and the lactate removal rates of the corresponding recovery conditions. These findings indicate that lactate increases proportionately with the metabolically active muscle mass, providing exercise remains aerobic. Thus in man, it appears that lactate removal from the blood during recovery exercise occurs primarily in skeletal muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00421713
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