The Brain Barrier System‐ii Uptake and Transport of Amino Acids by the Brain*

Lajtha, Ábel; Tóth, Jenő

doi:10.1111/j.1471-4159.1961.tb13545.x

Cited by 125 publications

(12 citation statements)

References 20 publications

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“…Our results are not in agreement with the results of Ondo et al [15], There is abundant evidence to indicate the existence of transport processes which act to clear amino acids from the cerebrospinal fluid to blood [4,6,7,9,10], Lorenzo [9] demonstrated that specific transport mechanisms existed for glycine and only the small fraction of glycine introduced into the ventricular cerebrospinal fluid was taken up by the brain. This suggests that the concen tration of glycine in the brain in the present study may be different from the concentration of glycine in the brain in the study of Ondo et al [ 15].…”

Section: Discussioncontrasting

confidence: 57%

Effects of Glycine on Serum Gonadotropins and Estradiol and on Concentrations of Free Amino Acids in the Middle Hypothalamus in Female Rats

Morishita¹,

Hashimoto²,

Kishi

et al. 1981

Gynecol Obstet Invest

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The effects of glycine on serum gonadotropins and estradiol (E₂) and on concentrations of free amino acids in the middle hypothalamus have been studied in diestrus-1 rats. 20 min after intraperitoneal administration, glycine in doses of 50 and 100 mg had no significant effect on serum luteinizing hormone (LH) levels, but 200 mg significantly elevated serum LH levels. Glycine in doses of 50–200 mg had no effect on serum follicle-stimulating hormone levels at 20 min after intraperitoneal injection. 200 mg of glycine significantly elevated serum LH levels at 20 and 50 min and serum E₂ levels at 50 and 80 min after intraperitoneal injection. The effects were maximal at 20 min after injection for LH and at 50 min after injection for E₂. 20 min after intraperitoneal injection, 200 mg of glycine significantly increased the concentration of glycine in the middle hypothalamus, but had no effect on the concentrations of the other free acidic and neutral amino acids in the middle hypothalamus. These results suggest that glycine may play a role in the neural regulation of LH secretion.

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Section: Discussioncontrasting

confidence: 57%

Effects of Glycine on Serum Gonadotropins and Estradiol and on Concentrations of Free Amino Acids in the Middle Hypothalamus in Female Rats

Morishita¹,

Hashimoto²,

Kishi

et al. 1981

Gynecol Obstet Invest

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“…4). The preferential entry of the L isomer of the naturally occuring amino acids into the brain has been shown previously (19)(20)(21)(22).…”

Section: Methodsmentioning

confidence: 99%

“…From morphological studies, the barrier to the diffusion of molecules into the brain and retina from the blood is believed to reside at the level of the microvascular endothelium with its tight junctions (1,4). Studies into the nature of the selective entry of substances into the brain have been reported using in vivo and in situ techniques (17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). From such studies it is known that nonpolar substances rapidly enter the brain by diffusion whereas polar molecules do not enter except by selective carrier systems (6).…”

Section: Discussionmentioning

confidence: 99%

Isolated microvessels: the blood-brain barrier in vitro.

Hjelle¹,

Baird-Lambert²,

Cardinale³

et al. 1978

Proc. Natl. Acad. Sci. U.S.A.

111

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Isolated bovine retinal and brain microvessels, exhibiting a patent lumen, were used to study the contribution of the microvasculature to the blood-brain and blood-retina barriers. The diffusion marker, sucrose, was taken up slowly by the isolated microvessels in contrast to leucine, tyrosine, and valine which were taken up at a considerably faster rate. Uptake of leucine was temperature dependent but resistant to inhibition by ouabain and sodium azide. The large neutral amino acids exhibited stereospecificity and cross-competition for uptake by the isolated microvessels. The apparent Kms for uptake for tyrosine, leucine, and valine were 111 M, 133 MM, and 500 M&M, respectively.The penetration into or removal of a substance from the central nervous system is a function of the interaction between that substance and the various brain barrier systems (1). These systems include the partitions between brain regions, various enzymatic barriers, the clearance and sink actions of the cerebrospinal fluid, choroid plexus and pial vessel transport, and partitioning at the blood-brain interface. From numerous morphological studies using dyes and electron-dense tracers, the barrier to the passage of substances from the blood into the brain has been thought to reside at the level of the intracerebral microvasculature (2). An indication that the microvascular endothelium, with its tight junctions, was the structural entity responsible for this barrier action and not the astrocytic processes adjacent to the microvessels was obtained when it was demonstrated that intraventricularly injected horseradish peroxidase appeared in the pericapillary space (3). Similarly, the impenetrability of the retinal microvasculature to dyes and electron-dense tracers (4) has been attributed to its endothelial tight junctions. In addition, both the retinal and brain microvascular endothelium have low rates of vesicle formation which further decreases the movement of molecules across this cell layer (5). Additional involvement of the cerebral microvasculature in blood-brain partitioning has been demonstrated by in situ carotid artery injection quickly followed by decapitation and determination of brain extraction of the injected test substance (6). Because of the short time interval between injection and decapitation, it has been assumed that the extraction of the test substance was an index of microvascular activity.To more directly characterize the role of the cerebral microvasculature in the partitioning of small molecules between the blood and the brain and to develop methods for the study of such phenomena in vitro, we examined isolated intracerebral bovine brain microvessels and the anatomically similar retinal microvessels for their abilities to exclude certain polar substances and to transport large neutral amino acids. Beef brains and enucleated eyes from yearling animals were obtained from a slaughterhouse, packed in ice, and taken to the laboratory within 30 min of death. MATERIALS AND METHODS MaterialsPreparation of Microvessels...

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“…The main system transporting leucine [1,8,9], in competition with the two other BCAA and aromatic amino acids, is the sodiumindependent L-type transporter [10]. This permease is present in both luminal and abluminal membranes of capillary endothelial cells [11].…”

Section: Transport Of Leucine and Of Intermediates Of Leucine Metabolismmentioning

confidence: 99%

Metabolic and Regulatory Roles of Leucine in Neural Cells

Murín

Hamprecht

2007

Neurochem Res

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Dietary leucine transported into the brain parenchyma serves several functions. Most prominent is the role of leucine as a metabolic precursor of fuel molecules, alpha-ketoisocaproate and ketone bodies. As alternatives to glucose, these compounds are forwarded by the producing astrocytes to the adjacent neural cells. Leucine furthermore participates in the maintenance of the nitrogen balance in the glutamate/glutamine cycle pertinent to the neurotransmitter glutamate. Leucine also serves as a regulator of the activity of some enzymes important for brain energy metabolism. Another role of leucine as an informational molecule is in mTOR signaling that participates in the regulation of food ingestion. The importance of leucine for brain function is stressed by the fact that inborn errors in its metabolism cause metabolic diseases often associated with neuropathological symptoms. In this overview, the current knowledge on the metabolic and regulatory roles of this essential amino acid in neural cells are briefly summarized.

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The Brain Barrier System‐ii Uptake and Transport of Amino Acids by the Brain*

Cited by 125 publications

References 20 publications

Effects of Glycine on Serum Gonadotropins and Estradiol and on Concentrations of Free Amino Acids in the Middle Hypothalamus in Female Rats

Effects of Glycine on Serum Gonadotropins and Estradiol and on Concentrations of Free Amino Acids in the Middle Hypothalamus in Female Rats

Isolated microvessels: the blood-brain barrier in vitro.

Metabolic and Regulatory Roles of Leucine in Neural Cells

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