Patterns of neutral amino acid uptake along rat small intestine

Baker, Richard G.; George, Mary

doi:10.1016/0005-2736(71)90225-2

Cited by 33 publications

(18 citation statements)

References 54 publications

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“…The differences among species may reflect the site of protein digestion and the availability of peptide substrates. The major site of amino acid absorption is recognized to be the jejunum in laboratory species such as the rat (Baker and George, 1971) and the ileum in sheep (Phillips et al, 1976(Phillips et al, , 1979 and cattle (Wilson and Webb, 1990). …”

Section: Discussionmentioning

confidence: 99%

Tissue distribution of a peptide transporter mRNA in sheep, dairy cows, pigs, and chickens.

Chen

Wong

Webb

1999

Journal of Animal Science

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Section: Discussionmentioning

confidence: 99%

Tissue distribution of a peptide transporter mRNA in sheep, dairy cows, pigs, and chickens.

Chen

Wong

Webb

1999

Journal of Animal Science

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“…Extremely slow accumulation of a-aminoisobutyric acid in the 2-day-old rat indicates that this nonmetabolized amino acid is transported by the imino acid-glycine pathway, as was first suggested by Akedo and Christensen [1]. Baker and George [3] have recently shown that the pattern of betaine and a-aminoisobutyric acid uptake along adult rat intestine is very similar, which further indicates that a-aminoisobutyric acid is transported by the same pathway as is used by betaine and sarcosine. The slow accumulation of a-aminoisobutyric acid can not be explained by loss of affinity for the primary neutral amino acid transport system because of the lack of a-hydrogen, since cycloleucine was actively accumulated.…”

Section: Discussionmentioning

confidence: 89%

“…The existence of two transport systems for neutral amino acids in mammalian small intestine is generally accepted [3,22,34]. One system has high affinity for neutral amino acids with lipophilic side chains, such as those listed in Table I.…”

Section: Resultsmentioning

confidence: 99%

“…One system has high affinity for neutral amino acids with lipophilic side chains, such as those listed in Table I. The second system has more affinity for imino acids, proline, glycine, and the Nsubstituted glycine derivatives such as betaine and sarcosine [3]. Proline and glycine probably have affinities for both neutral amino acid transport pathways [22].…”

Section: Resultsmentioning

confidence: 99%

“…2 Per cent of control value equals average intracellular accumulation of lysine in the presence of the added amino acid divided by that in absence of added amino acid. 3 Probability values were obtained by paired-difference t test. P < 0.05 was considered significant.…”

Section: Discussionmentioning

confidence: 99%

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Amino Acid Transport Pathways in the Small Intestine of the Neonatal Rat

1972

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ExtractThe activity of amino acid transport pathways in the small intestine of the 2-day-old rat was investigated. Transport was determined by measuring the uptake of 1 mM concentrations of various amino acids by intestinal segments after a 5-or 10-min incubation and it was expressed as intracellular accumulation.The neutral amino acid transport pathway was well developed with intracellular accumulation values for leucine, isoleucine, valine, methionine, tryptophan, phenylalanine, tyrosine, and alanine ranging from 3.9-5.6 mM/5 min. The intracellular accumulation of the hydroxy-containing neutral amino acids threonine (essential) and serine (nonessential) were 2.7 mM/5 min, a value significantly lower than those of the other neutral amino acids. The accumulation of histidine was also well below the level for the other neutral amino acids (1.9 mM/5 min). The basic amino acid transport pathway was also operational with accumulation values for lysine, arginine and ornithine ranging from 1.7-2.0 mM/5 min. Accumulation of the essential amino acid lysine was not statistically different from that of nonessential ornithine. Accumulation of aspartic and glutamic acid was only 0.24-0.28 mM/5 min indicating a very low activity of the acidic amino acid transport pathway. Accumulation of sarcosine and betaine was about 0.5 mM/5 min, which indicates a low activity for the imino acid-glycine pathway. The presence of 1 HIM alanine significantly (P < 0.01) increased the accumulation of lysine by 28.5%, which suggests the presence of an exchange transport system. These results show that by operation of the neutral and basic amino acid transport systems, the neonatal rat can effectively absorb all the essential amino acids; however, accumulation of individual amino acids appears to be governed by structural rather than nutritional considerations. SpeculationThe data presented demonstrate the differential ability of the neonatal rat to absorb various ammo acids. This finding is of potential importance in the formulation and evaluation of synthetic protein diets. IntroductionThe quality and quantity of dietary protein which would result in optimal growth and development of infants at a reasonable cost is a subject that has been discussed by nutritionists for several decades. Such discussion stimulated investigation of intestinal transport at, or shortly after birth [4-6, 13, 15, 30].A recent article by the authors [15] characterized the 713

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Transport of osmoprotective compounds in hybridoma cells exposed to hyperosmotic stress

et al. 1995

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Addition of osmoprotective compounds has a positive effect on growth and monoclonal antibody production in hyperosmotic hybridoma cell cultures. In order to better understand the processes involved in the osmoprotective response, uptake of the osmoprotective compounds glycine betaine, proline, sarcosine and glycine in mouse hybridoma cell line 6H11 during exposure to hyperosmotic stress was studied. Hyperosmotic stress (510 mOsmol/kg) was introduced through the addition of NaCl (100 mM) to the growth medium, and amino acid transport activity was measured immediately after transfer of the cells to the hyperosmotic medium. The osmoprotective capability of the four osmoprotectants tested was negatively affected if methylaminosobutyric acid (MeAiB), a specific substrate for amino acid transport system A, was simultaneously included in the hyperosmotic medium in equimolar amounts with one of the osmoprotective compounds. This was due to accumulation of MeAiB in the stressed cells, giving a significant reduction in the concentration of the osmoprotective compound inside the cells. Furthermore, addition of excess meAiB gave approx. 905 reduction in the initial rate of uptake of glycine betaine, while 40-50% reduction in the initial rate of uptake of proline, glycine and sarcosine. Similarly, addition of proline, glycine or sarcosine also gave a significant reduction in the initial rate of glycine betaine uptake. These results suggest that the four osmoprotective compounds share, at least in part, a common, MeAiB inhibitable carrier for transport into osmotically stressed hybridoma cells. This carrier is probably equal to amino acid transport system A.

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Patterns of neutral amino acid uptake along rat small intestine

Cited by 33 publications

References 54 publications

Tissue distribution of a peptide transporter mRNA in sheep, dairy cows, pigs, and chickens.

Tissue distribution of a peptide transporter mRNA in sheep, dairy cows, pigs, and chickens.

Amino Acid Transport Pathways in the Small Intestine of the Neonatal Rat

Transport of osmoprotective compounds in hybridoma cells exposed to hyperosmotic stress

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