The carrier reorientation step in erythrocyte choline transport: pH effects and the involvement of a carrier ionizing group

Devés, R.; Reyes, Guillermo Gotschlich; Krupka, Richard M.

doi:10.1007/bf01870808

Cited by 14 publications

(10 citation statements)

References 15 publications

(29 reference statements)

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“…Reyes & Krupka, 1986 Strategy used to calculate the kinetic parameters for two transport-systems using a selective inhibitor According to eqn (1) the effect of a competitive inhibitor on two transporters is determined by at least six kinetic parameters: two substrate half-saturation constants, two maximum rates and two inhibition constants. Even if the behaviour follows eqn (1) strictly, it would be difficult to justify attempting to fit data to an equation with so many unknowns.…”

Section: Methodsmentioning

confidence: 99%

Identification of a new transport system (y+L) in human erythrocytes that recognizes lysine and leucine with high affinity.

Devés¹,

Chávez²,

Boyd³

1992

The Journal of Physiology

162

113

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SUMMARY1. The effect of neutral amino acids on the transport of L-lysine across the human erythrocyte membrane was studied.2. All neutral amino acids tested (range 0 3-5 mM) inhibit the influx of L-[14C]lysine (1 /tM). The inhibition pattern is biphasic, and tends to reach a maximum at approximately 50 % of the original flux. The concentrations that give 25 % inhibition are (mM):L-lysine and Larginine completely inhibit the rate at the highest concentration.3. These results can be explained by assuming that L-lysine transport occurs through two independent transporters that differ in their affinity for neutral amino acids. A detailed kinetic analysis of the effect of L-leucine on L-lysine entry is consistent with this hypothesis.4. Using a new experimental strategy, the substrate and inhibitor transport parameters for the two systems were determined. The half-saturation constants for lysine (±S.E.M.) are found to be: KmA, 0-014+0-002 mm and KmB, 0 112+0-017 mM. The maximum rates differ by a factor of 8-2 (VmaXB/VmaxA). The leucine inhibition constants are: KiA, 0-022 + 0-003 mm and KiB, 30-36+7-9 mm. If the sodium in the incubation medium is replaced by potassium, the apparent affinity for leucine (1/KiA) is reduced approximately 30-fold.5. The maximum inhibition caused by leucine decreases as the lysine concentration is raised, showing that leucine acts upon the higher affinity system. 6. When added to the trans side, L-leucine, L-phenylalanine and L-isoleucine do not cause inhibition, but stimulate the flux by approximately 30%. This indicates that these analogues are also transported.7. In conclusion, in the concentration range 1-100 ,tM, lysine crosses the red cell membrane through two distinct transport systems, one of which recognizes both neutral and cationic amino acids with high affinity.MS 9679

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Section: Methodsmentioning

confidence: 99%

Identification of a new transport system (y+L) in human erythrocytes that recognizes lysine and leucine with high affinity.

Devés¹,

Chávez²,

Boyd³

1992

The Journal of Physiology

162

113

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“…Isoenzymes of PLD are produced by macrophages in human coronary plaques and colocalize with oxidation epitopes (69 ). Furthermore, early ischemic membrane damage and phospholipid breakdown by phospholipases (70 ) lead to release of choline into plasma followed by a secondary uptake into blood cells by a choline transport system (71 ).…”

Section: Cholinementioning

confidence: 99%

Future Biomarkers for Detection of Ischemia and Risk Stratification in Acute Coronary Syndrome

et al. 2005

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Background: Evaluation of patients who present to the hospital with a complaint of chest pain or other signs or symptoms suggestive of acute coronary syndrome (ACS) is time-consuming, expensive, and problematic. Recent investigations have indicated that increases in biomarkers upstream from biomarkers of necrosis (cardiac troponins I and T), such as inflammatory cytokines, cellular adhesion molecules, acute-phase reactants, plaque destabilization and rupture biomarkers, biomarkers of ischemia, and biomarkers of myocardial stretch may provide earlier assessment of overall patient risk and aid in identifying patients with higher risk of an adverse event.

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“…Both of these processes could result in choline release into the plasma. Plasma choline is subsequently taken up by erythrocytes via a choline transporter [7,8] . Choline release is believed to occur very early during ischaemia.…”

mentioning

confidence: 99%

Biomarkers of Cardiovascular Damage

Collinson¹,

Gaze²

2007

Med Princ Pract

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Acute coronary syndromes (ACS) are due to the rupture or erosion of atheromatous plaques. This produces, depending on plaque size, vascular anatomy and degree of collateral circulation, progressive tissue ischaemia which may progress to cardiomyocyte necrosis. This may then result in cardiac remodelling. Serum biomarkers are available which can be used for diagnosis of all of these stages. Markers to detect myocardial ischaemia at the pre-infarction stage are potentially the most interesting but also the most challenging. An ischaemia marker offers the opportunity to intervene to prevent progression to infarction. The problems with potential ischaemia markers are specificity and the reference diagnostic standard against which they can be judged. To date, only one, ischaemia-modified albumin®, has reached the point where clinical studies can be performed. The measurement of the cardiac troponins, cardiac troponin T and cardiac troponin I, have become recognised as the diagnostic reference standard for myocardial necrosis. The sensitive nature of these tests has also revealed that myocardial necrosis is also found in a range of other clinical situations, highlighting the need to use all clinical information for diagnosis of acute myocardial infarction. The measurement of B-type natriuretic peptides can be shown to be diagnostic and prognostic in both ACS and detecting the sequelae of post-infarction myocardial insufficiency. The role of the B-type natriuretic peptides in detection of cardiac failure, both acute and chronic, is well defined but remains the subject of further studies, in ACS.

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The carrier reorientation step in erythrocyte choline transport: pH effects and the involvement of a carrier ionizing group

Cited by 14 publications

References 15 publications

Identification of a new transport system (y+L) in human erythrocytes that recognizes lysine and leucine with high affinity.

Identification of a new transport system (y+L) in human erythrocytes that recognizes lysine and leucine with high affinity.

Future Biomarkers for Detection of Ischemia and Risk Stratification in Acute Coronary Syndrome

Biomarkers of Cardiovascular Damage

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