Production of free glutamate in milk requires the leucine transporter LAT1

2013 ◽  
Vol 305 (6) ◽  
pp. C623-C631 ◽  
Author(s):  
Takuya Matsumoto ◽  
Eiji Nakamura ◽  
Hidehiro Nakamura ◽  
Mariko Hirota ◽  
Ana San Gabriel ◽  
...  
Keyword(s):  
Amino Acids ◽  
Transport System ◽  
Active Role ◽  
Mammary Tissue ◽  
Limiting Factor ◽  
Mammary Cells ◽  
Oral Gavage ◽  
Uptake Inhibition ◽  
Umami Taste

The concentration of free glutamate (Glu) in rat's milk is ∼10 times higher than that in plasma. Previous work has shown that mammary tissue actively transports circulatory leucine (Leu), which is transaminated to synthesize other amino acids such as Glu and aspartate (Asp). To investigate the molecular basis of Leu transport and its conversion into Glu in the mammary gland, we characterized the expression of Leu transporters and [3H]Leu uptake in rat mammary cells. Gene expression analysis indicated that mammary cells express two Leu transporters, LAT1 and LAT2, with LAT1 being more abundant than LAT2. This transport system is sodium independent and transports large neutral amino acids. The Leu transport system in isolated rat mammary cells could be specifically blocked by the LAT1 inhibitors 2-aminobicyclo-[2.2.1]-heptane-2-carboxylic acid (BCH) and triiodothyronine (T3). In organ cultures, Glu secretion was markedly inhibited by these LAT1 inhibitors. Furthermore, the profiles of Leu uptake inhibition by amino acids in mammary cells were similar to those reported for LAT1. In vivo, concentrations of free Glu and Asp increased in milk by oral gavage with Leu at 6, 12, and 18 days of lactation. These results indicate that the main Leu transporter in mammary tissue is LAT1 and the transport of Leu is a limiting factor for the synthesis and release of Glu and Asp into milk. Our studies provide the bases for the molecular mechanism of Leu transport in mammary tissue by LAT1 and its active role on free Glu secretion in milk, which confer umami taste in suckling pups.

Steps in amino-acid incorporation into mammary tissue

1958 ◽  
Vol 149 (936) ◽  
pp. 392-400 ◽  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Mammary Gland ◽  
Amino Acid ◽  
De Novo ◽  
Protein Biosynthesis ◽  
Mammary Tissue ◽  
Mammary Cells ◽  
Intact Cells ◽  
Ideal System

The mammary gland in full lactation had for long been recognized as an ideal system for the study of the biosynthesis of protein. The discoveries during the last 5 years of the incorporation of labelled amino acids into the microsomes of cell homogenates and of other reactions of amino acids which might be on the pathway to protein synthesis, encouraged us to study the fate of amino acids in various systems prepared from mammary cells. De novo protein synthesis had not yet been proved in any system which contained no intact cells. So far no net increase in any defined protein fraction during incubations has been found or indeed looked for in our experiments. Naturally one hopes that such studies of the fate of labelled amino acids in cell-free preparations will reveal the detail of enzymic reactions which will prove to be part of the mechanisms of protein biosynthesis. Three types of reactions of amino acids in cell-free preparations from homogenates of many tissues have been studied most extensively. (1) The acyl activation of amino acids to form amino acid-acid adenylates in the presence of ATP and ‘activating enzymes’. (2) The formation of compounds of cell sap-ribonucleic acid ( SRN A ) with amino acids in the presence of ATP and ‘activating enzymes’. (3) The incorporation of amino acids into intracellular particles either from free amino acid or by transfer from amino-acid- SRN A compounds in the presence of ATP , guanosine triphosphate ( GTP ) and ‘activating enzymes’. In this paper we are giving a survey of the results of studies on these three types of reactions in systems prepared from mammary tissue and we are relating these to results obtained with other systems elsewhere. Some comparative studies of the incorporation of labelled amino acids into protein fractions of intact mammary cells (minced tissue) are also presented. All the original results given here were obtained from experiments with guinea-pig mammary gland preparations from animals 2 to 6 days after parturition. Experimental detail will be reported elsewhere.

Intestinal transport of certain N-substituted amino acids

1962 ◽  
Vol 203 (4) ◽  
pp. 637-640 ◽  
Author(s):  
Hiroshi Hagihira ◽  
T. Hastings Wilson ◽  
Edmund C. C. Lin
Keyword(s):  
Amino Acids ◽  
Transport System ◽  
Intestinal Transport ◽  
Transport Systems ◽  
Concentration Gradients ◽  
Methyl Derivatives ◽  
Derivatives Of ◽  
Amino Acid Carrier ◽  
Everted Sacs

Sarcosine, N,N-dimethylglycine and betaine were transported against concentration gradients by everted sacs of hamster small intestine. These compounds shared a common transport system which differed from that which acted on most neutral l-amino acids. The N-methyl derivatives of glycine, while competing with each other, had no effect on the transport of l-valine. Furthermore, l-valine and l-methionine, which were powerful inhibitors of the transport of most other neutral l-amino acids, had little effect on the absorption of betaine. Two other N-substituted amino acids, l-proline and hydroxy-l-proline, possessed affinity for both transport systems, a greater affinity being shown for the betaine carrier than for the neutral amino acid carrier. It is postulated that the transport system for N-substituted amino acids is important for the absorption of l-proline and hydroxy-l-proline in vivo.

scholarly journals How Glutamate Is Managed by the Blood-Brain Barrier

2016 ◽  
Author(s):  
Richard A. Hawkins ◽  
Juan R. Viña
Keyword(s):  
Amino Acids ◽  
Blood Brain Barrier ◽  
Transport System ◽  
Glutamate Transporter ◽  
Extracellular Fluid ◽  
Circumventricular Organs ◽  
Brain Barrier ◽  
Transport Systems ◽  
Blood Brain

A facilitative transport system exists on the blood brain barrier (BBB) that has been tacitly assumed to be a path for glutamate entry to brain. But glutamate is a non-essential amino acid whose brain content is much greater than plasma, and studies in vivo show that glutamate does not enter brain in material quantities except in those small regions with fenestrated capillaries (circumventricular organs). The situation became understandable when luminal (blood facing) and abluminal (brain facing) membranes were isolated and studied separately. Facilitative transport of glutamate and glutamine exist only on the luminal membranes whereas Na+-dependent transport systems for glutamate, glutamine and some other amino acids are present only on the abluminal membrane. The Na+-dependent cotransporters of the abluminal membrane are in a position to actively transport amino acids from the extracellular fluid (ECF) into the endothelial cells of the BBB. These powerful secondary active transporters couple the energy of the Na+-gradient to move glutamate and glutamine into the ECF whereupon glutamate can exit to blood on the luminal facilitative glutamate transporter. Glutamine may also exit brain on a separate facilitative transport system that exists on the luminal membranes or glutamine can be hydrolyzed to glutamate within the BBB thereby releasing ammonia that is freely diffusible. The γ-glutamyl participate cycle participates indirectly by producing oxoproline (pyroglutamate) that stimulates almost all secondary active transporters yet discovered in the abluminal membranes of the BBB.

Identification of a high affinity taurine transporter which is not dependent on chloride

1995 ◽  
Vol 15 (4) ◽  
pp. 231-239 ◽  
Author(s):  
D. B. Shennan
Keyword(s):  
Amino Acids ◽  
Transport System ◽  
Niflumic Acid ◽  
Cell Swelling ◽  
Mammary Tissue ◽  
Taurine Transporter ◽  
Taurine Transport ◽  
High Affinity ◽  
Taurine Uptake

Taurine transport by lactating gerbil mammary tissue has been examined. Taurine uptake is, mediated by a high-affinity system which is specific for β-amino acids. The uptake of taurine is Na+-dependent but appears not to be obligatorly dependent upon Cl−. Thus, replacing Na+ with choline almost abolished taurine uptake. Substituting Cl− with NO3− had no effect whereas SCN− induced a small but significant increase in taurine influx. Taurine uptake was Na+-dependent under conditions where Cl− had been replaced with NO3−. However, it is apparent that the Na+-dependent taurine transport system requires the presence of a permeable anion because replacing Cl− with gluconate markedly reduced taurine uptake. Cell-swelling, induced by a hyposmotic challenge, increased the efflux of taurine from gerbil mammary tissue via a pathway sensitive to niflumic acid.

scholarly journals Glutathione utilization by lactating bovine mammary secretory tissue in vitro

1981 ◽  
Vol 198 (1) ◽  
pp. 243-246 ◽  
Author(s):  
C R Baumrucker ◽  
P A Pocius ◽  
T L Riss
Keyword(s):  
Amino Acids ◽  
Milk Protein ◽  
Mammary Tissue ◽  
Mammary Cells ◽  
Tissue Uptake ◽  
Radioactive Label ◽  
Gamma Glutamyltransferase ◽  
Secretory Tissue ◽  
Glutamyl Transpeptidase

gamma-Glutamyltransferase (D-glutamyl transpeptidase, EC 2.3.2.2) activity has been shown to be located predominantly on the extracellular surface of the plasma membrane of lactating bovine mammary cells. Radioactive label from both oxidized ([14C]-gamma-glutamyl) and reduced ([35S]cysteinyl) glutathione was taken up and incorporated into acid-precipitable proteins of mammary tissue. Uptake was shown to involve the transport of free amino acids, and incorporation was shown to involve the action of gamma-=glutamyltransferase. These results indicate that lactating mammary tissue utilizes the constituent amino acids of glutathione for milk-protein synthesis.

The transport of L-leucine into the brain of the rat in vivo : saturable and non-saturable components of influx

1977 ◽  
Vol 196 (1124) ◽  
pp. 333-346 ◽  
Keyword(s):  
Amino Acids ◽  
Transport System ◽  
Normal Level ◽  
Transport Process ◽  
Minor Component ◽  
Carrier Mediated Transport ◽  
A Minor ◽  
Osmotic Effects ◽  
The Brain

The influx of L-leucine into the brain was measured under normal conditions, and also when its concentration in the circulation was progressively increased. The transport system carrying L-leucine into the brain could be saturated, but the results only conformed to Michaelis kinetics if a nonsaturable component was first subtracted from the observed influx data. The proportion of the total influx due to this non-saturable component was small, but it increased as the concentration of leucine in the blood was raised above the normal level. The saturable component of the influx of leucine could be inhibited by raising the concentration of L-valine in the blood, but the influx of leucine into the brain could not be reduced to zero. The residual influx of leucine in the presence of the inhibitor was in part, due to leucine competing with the inhibitor, valine, for the shared carrier, but it was also in part due to the non-saturable component of leucine influx, which is unaffected by the inhibitor. Thus there are two components in the influx of leucine into the brain: a major component, which is a carrier-mediated transport process, and a minor component which is non-saturable. The possibility of a nonsaturable component of the transport of amino acids into the brain has not previously been considered. The non-saturable component may be due to diffusion through the cerebral capillaries in small regions of the brain where the endothelium is permeable; osmotic effects may also contribute. The findings may be of importance in the treatment of aminoacidaemias.

Formation and Structure of Casein Micelles in Lactating Mammary Tissue

1970 ◽  
Vol 28 ◽  
pp. 150-151
Author(s):  
Robert J. Carroll ◽  
Marvin P. Thompson ◽  
Harold M. Farrell
Keyword(s):  
Size Distribution ◽  
G Protein ◽  
Milk Proteins ◽  
Mammary Tissue ◽  
Colloidal System ◽  
Casein Micelles ◽  
The Stability

Milk is an unusually stable colloidal system; the stability of this system is due primarily to the formation of micelles by the major milk proteins, the caseins. Numerous models for the structure of casein micelles have been proposed; these models have been formulated on the basis of in vitro studies. Synthetic casein micelles (i.e., those formed by mixing the purified αsl- and k-caseins with Ca2+ in appropriate ratios) are dissimilar to those from freshly-drawn milks in (i) size distribution, (ii) ratio of Ca/P, and (iii) solvation (g. water/g. protein). Evidently, in vivo organization of the caseins into the micellar form occurs in-a manner which is not identical to the in vitro mode of formation.

Cytological changes induced by platinum-thymine in sarcoma-180 cells: Electron microscopy study

1990 ◽  
Vol 48 (3) ◽  
pp. 290-291
Author(s):  
Gustav Ofosu
Keyword(s):  
Mammalian Cells ◽  
Antitumor Agent ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Limiting Factor ◽  
Sarcoma 180 ◽  
Electron Microscopic ◽  
Cytological Changes

Platinum-thymine has been found to be a potent antitumor agent, which is quite soluble in water, and lack nephrotoxicity as the dose-limiting factor. The drug has been shown to interact with DNA and inhibits DNA, RNA and protein synthesis in mammalian cells in vitro. This investigation was undertaken to elucidate the cytotoxic effects of piatinum-thymine on sarcoma-180 cells in vitro ultrastructurally, Sarcoma-180 tumor bearing mice were treated with intraperitoneal injection of platinum-thymine 40mg/kg. A concentration of 60μg/ml dose of platinum-thymine was used in in vitro experiments. Treatments were at varying time intervals of 3, 7 and 21 days for in vivo experiments, and 30, 60 and 120 min., 6, 12, and 24th in vitro. Controls were not treated with platinum-thymine.Electron microscopic analyses of the treated cells in vivo and in vitro showed drastic cytotoxic effect.

Potential Uses of Vinegar as a Medicine and Related in vivo Mechanisms

2016 ◽  
Vol 86 (3-4) ◽  
pp. 127-151 ◽  
Author(s):  
Zeshan Ali ◽  
Zhenbin Wang ◽  
Rai Muhammad Amir ◽  
Shoaib Younas ◽  
Asif Wali ◽  
...  
Keyword(s):  
Chemical Structure ◽  
Review Paper ◽  
Heart Diseases ◽  
Folk Medicine ◽  
Active Role ◽  
Current Review ◽  
Different Types ◽  
Positive Effect

While the use of vinegar to fi ght against infections and other crucial conditions dates back to Hippocrates, recent research has found that vinegar consumption has a positive effect on biomarkers for diabetes, cancer, and heart diseases. Different types of vinegar have been used in the world during different time periods. Vinegar is produced by a fermentation process. Foods with a high content of carbohydrates are a good source of vinegar. Review of the results of different studies performed on vinegar components reveals that the daily use of these components has a healthy impact on the physiological and chemical structure of the human body. During the era of Hippocrates, people used vinegar as a medicine to treat wounds, which means that vinegar is one of the ancient foods used as folk medicine. The purpose of the current review paper is to provide a detailed summary of the outcome of previous studies emphasizing the role of vinegar in treatment of different diseases both in acute and chronic conditions, its in vivo mechanism and the active role of different bacteria.

An Attempt at Biological Control of Blossom Blight of Rose Caused by Botrytis cinerea Using some Local Trichoderma spp. Strains

2020 ◽  
Vol 55 (1) ◽  
pp. 27-34
Author(s):  
G. Zadehdabagh ◽  
K. Karimi ◽  
M. Rezabaigi ◽  
F. Ajamgard
Keyword(s):  
Botrytis Cinerea ◽  
Mycelial Growth ◽  
Limiting Factor ◽  
Dual Culture ◽  
Trichoderma Spp ◽  
Khuzestan Province ◽  
Inhibitory Potential ◽  
Cut Rose

The northern of Khuzestan province in Iran is mainly considered as one of the major areas of miniature rose production. Blossom blight caused by Botrytis cinerea has recently become a serious limiting factor in rose production in pre and post-harvest. In current study, an attempt was made to evaluate the inhibitory potential of some local Trichoderma spp. strains against B. cinerea under in vitro and in vivo conditions. The in vitro results showed that all Trichoderma spp. strains were significantly able to reduce the mycelial growth of the pathogen in dual culture, volatile and non-volatile compounds tests compared with control, with superiority of T. atroviride Tsafi than others. Under in vivo condition, the selected strain of T. atroviride Tsafi had much better performance than T. harzianum IRAN 523C in reduction of disease severity compared with the untreated control. Overall, the findings of this study showed that the application of Trichoderma-based biocontrol agents such as T. atroviride Tsafi can be effective to protect cut rose flowers against blossom blight.

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