Amino Acid Transport

Oja, Simo S.; Korpi, Esa R.

doi:10.1007/978-1-4899-4555-6_15

Cited by 18 publications

(4 citation statements)

References 218 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The K, values for alanine are within the range of those found in various central nervous tissues for the "low-affinity'' uptake of other neutral amino acids, namely glycine, leucine, tyrosine, and phenylalanine, which are mostly between 0.3 and 5 mM. However, the values found are much greater than those reported for the "high-affinity" uptakes of the same acids, which lie between 0.004 and 0.06 mM (Oja and Korpi, 1983). It is possible that the rather wide ranges of published values would have been narrower if more attention had been paid to concentration gradients and to possible reuptake of released material.…”

Section: Half-saturation Concentrations For Uptake (K)supporting

confidence: 65%

Extracellular Intermediates of Glucose Metabolism: Fluxes of Endogenous Lactate and Alanine Through Extracellular Pools in Embryonic Sympathetic Ganglia

Larrabee

1992

Journal of Neurochemistry

View full text Add to dashboard Cite

The flux rates of lactate and alanine in and out of the cells of an intact tissue, which cannot be measured directly because some of the released materials are reabsorbed, were determined by computer analysis of uptakes and outputs by the whole tissue in the presence of various concentrations of these substances. The outputs of labeled lactate and alanine from [U-14C]glucose and the uptakes of [U-14C]lactate and [U-14C]alanine were measured on intact sympathetic ganglia excised from 15-day-old chicken embryos. The volume and time constant of the extracellular space were measured using labeled lactate, alanine, and sucrose. Models, which mathematically described the cellular uptakes and outputs as functions of the extracellular concentrations, were used to predict the exchanges that would be observed on the whole tissue, and their parameters were adjusted for best fit to the actual observations. The fitted models were then used to calculate the fluxes in and out of the cells and the concentrations in the extracellular space. The following results were obtained: (1) Cellular uptakes of lactate and alanine were both well described by familiar Michaelis-Menten kinetics. (2) The cellular output of [14C]-lactate from [14C]glucose declined with increase in the extracellular lactate concentration, whereas the cellular output of [14C]alanine from [14C]glucose rose with the extracellular alanine concentration. (3) Half-saturation values for cellular uptake, determined from the fitted equations, were 0.45 mM for lactate and 1.17 mM for alanine, both several-fold lower than less relevant estimates for the whole tissue made directly from the uptake observations. (4) As much as 45% of the carbon in the glucose consumed was released into the extracellular space as lactate and alanine, but much of this was reabsorbed. Implications for brain metabolism are discussed.

show abstract

Section: Half-saturation Concentrations For Uptake (K)supporting

confidence: 65%

Extracellular Intermediates of Glucose Metabolism: Fluxes of Endogenous Lactate and Alanine Through Extracellular Pools in Embryonic Sympathetic Ganglia

Larrabee

1992

Journal of Neurochemistry

View full text Add to dashboard Cite

show abstract

“…In keeping with the present results, the influx of aromatic amino acids, which are mainly served by the same transport sites as the branched-chain amino acids (Oja & Korpi 1983). also increased into rat cerebral cortex slices during postnatal development (Vahvelainen & Oja 1972).…”

Section: Discussionsupporting

confidence: 91%

“…The same transport sites are assumed to take part in both influx and exchange processes (Battistin et at. 1972) and the transport system L is particularly prone to exchange (Oja & Korpi 1983) The author thanks Prof. Simo S. Oja for criticism of the manuscript. Dr Kirsi-Maja Mamela for expert help with amino acid analyses and Ms Pirkko Luoma and Ms Irma Rantamaa for their skilful technical assistance.…”

mentioning

confidence: 99%

Transport of branched‐chain amino acids in brain slices of developing and adult rats

Pajari

1984

Acta Physiologica Scandinavica

View full text Add to dashboard Cite

The accumulation of labelled leucine, isoleucine and valine by cerebral slices of developing and adult rats was studied. The accumulation increased with age by 15-25%. It was strongly (from 52 to 86%) inhibited by a 100-fold excess of phenylalanine, tryptophan and another branched-chain amino acid, but moderately activated by GABA and glutamate. The inhibitions evoked by leucine and isoleucine were slightly stronger in young than in adult rats. The corresponding 2-oxoacid analogs of leucine, isoleucine and valine were also inhibitory but less effective. The 30-min accumulation of 3H-labelled branched-chain amino acids was ostensibly higher than the increase in their total concentrations in incubated slices, which apparently bespeaks lively homoexchange of endogenous intracellular and labelled extracellular amino acids.

show abstract

“…Par tially restored blood flow may help delivery of tracer amino acid. The mechanism for an increased level of free amino acid may be explained by the increase in the capillary permeability of pathologic vessels (Kobayashi et aI., 1975) or by the activated carrier-mediated transport of amino acid (Letendre et aI., 1980;Oja and Korpi, 1983). However, it is not determined in this study whether or not the in crease in free tracer is a consequence of such kinds of accelerated amino acid uptake, or merely a re flection of decreased consumption of tracer due to the inhibited incorporation of amino acid into poly peptide.…”

Section: Discussionmentioning

confidence: 99%

Autoradiographic Study of Regional Protein Synthesis in Focal Cerebral Ischemia with TCA Wash and Image Subtraction Techniques

Yoshimine

Hayakawa

Kato

et al. 1987

J Cereb Blood Flow Metab

View full text Add to dashboard Cite

Summary:The standard biochemical method of trichlor acetic acid (TCA) wash and the image processing tech nique were combined to differentiate and visualize the distributions of polypeptide-incorporated and unincor porated tracers in an autoradiographic study of regional protein synthesis, The validity of applying TCA wash procedures to cryostat sections was considered by histo logic and chemical evaluations, For the autoradiographic study of in vivo protein synthesis, a tracer dose of L-[14C]valine was administered 30 min after occlusion of the posterior communicating artery in gerbils. Images of total (polypeptide-incorporated and unincorporated) ra dioactivity and of polypeptide-incorporated radioactivity were obtained from an identical cryostat section before As unexpected heterogeneity in tracer delivery may lead to an erroneous interpretation of the rate of polypeptide synthesis, the distributions of not only incorporated tracers, but also of unincorpor ated tracers, are important in the autoradiographic study of in vivo protein metabolism. However, at tention has not been fully paid to the latter fraction, in contrast to that given to the incorporated fraction (Dienel et aI., 1980;Kiessling and Kleihues, 1981;Dwyer et al., 1982;Hossmann et al. , 1983;Kiessling et al. 1984). The purpose of this article is to develop the method and to study the distribu tions of these two fractions in an identical autora diographic section. The first half of this article eval- 387and after TCA wash. The polypeptide-unincorporated ra dioactivity image was produced with an image processing system by subtracting pixel by pixel the polypeptide-in corporated radioactivity from the total radioactivity. The present study clearly demonstrated that in spite of the sufficient delivery of tracer amino acids, the polypeptide synthesis was completely lost in the ischemic focus. Free tracer was markedly accumulated in the brain adjacent to the ischemic focus. This kind of autoradiographic tech nique seems to be indispensable in studying the topo graphical complexity of the altered protein metabolism in the pathologic brain. Key Words: Image processing Mongolian gerbil-Protein metabolism-Quantitative autoradiography-Regional cerebral ischemia-Valine.uates the applicability of the standard biochemical trichloracetic acid (TeA) wash procedures to cryostat sections in distinguishing the two frac tions. In the rest of the paper, TeA wash method was combined with an image subtraction technique (Kato et aI. , 1985) to demonstrate the topographic changes in protein metabolism in a gerbil brain after occlusion of the posterior communicating artery (Yoshimine and Yanagihara, 1983). MATERIALS AND METHODSMongolian gerbils (Meriones unguiculatus), weighing 60-70 g each, were anesthetized with intraperitoneal in jection of ketamine hydrochloride (80 mg/kg) at the be ginning of the following experiments. Effect of TeA wash on tissue morphologyAs TCA wash procedures may cause detachment of sections from coverslips, or may affect the size and shape of t...

show abstract

Amino Acid Transport

Cited by 18 publications

References 218 publications

Extracellular Intermediates of Glucose Metabolism: Fluxes of Endogenous Lactate and Alanine Through Extracellular Pools in Embryonic Sympathetic Ganglia

Extracellular Intermediates of Glucose Metabolism: Fluxes of Endogenous Lactate and Alanine Through Extracellular Pools in Embryonic Sympathetic Ganglia

Transport of branched‐chain amino acids in brain slices of developing and adult rats

Autoradiographic Study of Regional Protein Synthesis in Focal Cerebral Ischemia with TCA Wash and Image Subtraction Techniques

Contact Info

Product

Resources

About