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  • 1
    Electronic Resource
    Electronic Resource
    Effect of regular training on the myocardial and plasma concentrations of taurine andα-amino acids in thoroughbred horses (1998)
    Springer
    Amino acids 15 (1998), S. 241-251 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Taurine ; Protein amino acids ; Thoroughbred horses ; Heart ; Plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Exercise induces significant changes in the free intracellular amino acid pool in skeletal muscle but little is known of whether such changes also occur in cardiac muscle. In this study the effect of regular exercise on the size and the constituents of the free amino acid pool in the hearts and in the plasma of thoroughbred horses was investigated. The total free intracellular amino acid pool in the hearts of control horses was 30.9 ± 1.2μmol/g wet weight (n = 6). Glutamine but not taurine was present at the highest concentration (13.5 ± 0.9 and 7.7 ± 0.69μmol/g wet weight for glutamine and taurine respectively). As for the rest of the amino acids in the pool, only glutamate and alanine were present at levels greater than 1μmol/g wet weight (4.6 ± 0.25 and 1.7 ± 0.14 for glutamate and alanine respectively). The tissue to plasma ratio was highest for taurine at 155, followed by glutamate at 111, aspartate and glutamine at 37, alanine at 5.8 and ratios of less than 3 for the rest of the amino acids. The total free intracellular amino acid pool in the hearts of exercised horses was slightly but not significantly lower than control (28.1 ±1.1μmol/g wet weight, n = 6). Regular exercise increased the intracellular concentration of threonine, valine, isoleucine, leucine and phenylalanine but was only significant (p 〈 0.05) for threonine. This work has documented the profile of taurine and protein amino acids in the heart and in the plasma of thoroughbred horses and showed that in contrast to skeletal muscle, heart muscle does not show major changes in amino acids during regular exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01318863
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  • 2
    Electronic Resource
    Electronic Resource
    Co-expression of an anion conductance pathway with Na+-glucose cotransport in rat renal brush-border membrane vesicles (1993)
    Springer
    Pflügers Archiv 423 (1993), S. 406-410 
    Details
    ISSN: 1432-2013
    Keywords: Brush border ; Membrane vesicle ; Cl− conductance ; Cystic fibrosis transmembrane regulator ; Na-glucose cotransport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Brush-border membrane vesicles were prepared from superficial rat renal cortex by a Mg2+-precipitation technique. The initial (20 s) [14C]glucose uptake rate from solutions containing 100 mmol/l Na (salt) was found to be dependent upon the anion composition of the medium; in comparison to gluconate-containing medium (0.46±0.05 nmol/mg protein), Cl− accelerated the initial rate to 1.47±0.21 nmol/mg protein (n=4 preparations, ± SEM). This enhancement was reduced by 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB, 0.5 mmol/l), but was unaffected by 4,4′-diisothiocyanatostilbene 2,2′-disulphonate (DIDS, 0.5 mmol/l). When membrane vesicles were pre-equilibrated with 100 mmol/l K (salt) and 100 mmol/l mannitol and glucose uptake was measured from a solution containing 100 mmol/l Na gluconate and 100 mmol/l mannitol in the presence of 80 μmol/l valinomycin (to generate an outward K+ diffusion electrical p. d.), it was found that intravesicular KCl depressed the initial glucose uptake compared to K gluconate. NPPB (0.5 mmol/l) increased the initial glucose uptake with intravesicular KCl towards values seen in K gluconate vesicles. In conditions where the only driving force for glucose uptake was established by an inward anion gradient (Nao=Nai) it was found that inward Cl− gradients could drive uphill glucose transport and that this was sensitive to NPPB (0.5 mmol/l), but insensitive to DIDS. We conclude that a Cl− conductance co-exists with Na-cotransport in rat renal brush-border membrane vesicles prepared from superficial renal cortex and this may function to regulate the activity of electrogenic transport systems at this membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374934
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  • 3
    Electronic Resource
    Electronic Resource
    The intrinsic Cl–conductance of mouse kidney cortex brush-border membrane vesicles is not related to CFTR (1997)
    Springer
    Pflügers Archiv 434 (1997), S. 575-580 
    Details
    ISSN: 1432-2013
    Keywords: Key words Brush-border ; Membrane vesicle ; Cystic fibrosis transmembrane regulator (cftr) ; Alternate Cl ; conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstracts  Brush-border membrane vesicles (BBMV) were prepared from whole Balb/c mice kidneys by a Mg2+ precipitation technique. The presence of an intrinsic Cl–conductance co-expressed with Na+/glucose cotransport was inferred by the anion dependence of [14C]glucose uptake and overshoot with inward Na+-anion gradients. In Na+-equilibrated conditions, an inside-negative membrane potential difference (p.d.) produced by an inward Cl–gradient alone was capable of driving intravesicular [14C]glucose accumulation. The apparent anion conductance had a selectivity of Br– = I– = Cl– 〉  F–〉〉 gluconate, was inhibited by 0.5 mM 5-nitro-2- (3-phenylpropylamino)-benzoic acid (NPPB) but was unaffected by 0.5 mM 4,4′-diisothiocyanatostilbene 2,2′-disulphonate (DIDS). BBMV were isolated from mice in which the CFTR gene had been disrupted by a termination mutation (–/–) and compared with normal litter mates (+/+) and heterozygotes (–/+)[18]. [14C]Glucose uptake in NaCl media was significantly greater than glucose uptake in Na gluconate media for all three genotypes measured at 20 s: for homozygous –/– animals [14C]glucose uptake was increased by 2.80 ± 0.53 fold in Cl–media compared to gluconate media, n = 6; for wild-type +/+, by 2.16 ± 0.53 fold, n = 8; and for heterozygous +/– animals, by 2.17 ± 0.45 fold, n = 8. The observation of a Cl–-dependent component in BBMV isolated from homozygous –/– mutant animals shows that the chloride conductance in these vesicles cannot be due to cftr expression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050438
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    Paper (German National Licenses)
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