Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Evidence for Active Transport of Melphalan by Two Amino Acid Carriers in L5178Y Lymphoblasts in Vitro

Evidence for Active Transport of Melphalan by Two Amino Acid Carriers in L5178Y Lymphoblasts in... Investigation of the mechanism of uptake of melphalan by L5178Y lymphoblasts has been extended with particular emphasis on the chemical specificity of the transport mechanism. Evidence was obtained that uptake of melphalan was an active carrier-mediated process. Uptake appeared to proceed "uphill" against a concentration gradient of approximately eight-fold and was temperature sensitive, partly sodium dependent, and inhibited by ouabain and p -hydroxymercuribenzoate. Drug uptake followed biphasic Michaelis-Menten kinetics suggesting the involvement of at least two carrier systems and was markedly inhibited by a variety of amino acids. Melphalan uptake was strongly inhibited by ß-2-aminobicyclo2,2,1heptane-2-carboxylic acid, a specific inhibitor of the L amino acid transport (leucine-preferring) system but not by 2-aminoisobutyric acid or 2-(methylamino)-isobutyric acid, specific inhibitors of the A amino acid (alanine-preferring) system. Under conditions in which the L and A systems were saturated by ß-2-aminobicyclo-2,2,1heptane-2-carboxylic acid and 2-aminoisobutyric acid, drug uptake was inhibited by serine, an amino acid known to be transported by the ASC (alanine, serine, and cysteine) system. In reciprocal experiments with leucine as substrate, melphalan inhibited uptake of the amino acid by both the L system and a second system resembling ASC. All of the carrier-mediated uptake of melphalan could be accounted for by transport on these two systems. In the drug concentration range of 3.33 to 20 µ M , carriermediated uptake of melphalan appeared to be almost equally divided between the L system and the system resembling ASC, while in the 20 to 100 µ M concentration range, uptake by the L system became increasingly dominant. Uptake of melphalan by the L carrier system had a K m of 8.0 ± 3.0 x 10 -5 M and a V max of 1.1 ± 0.4 x 10 -16 mol/cell/min, while uptake by the second system had a K m of 1.0 ± 0.7 x 10 -5 M and a V max of 2.2 ± 2.4 x 10 -17 mol/cell/min. 1 This work was supported by a grant from the National Cancer Institute of Canada. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Cancer Research American Association of Cancer Research

Evidence for Active Transport of Melphalan by Two Amino Acid Carriers in L5178Y Lymphoblasts in Vitro

Evidence for Active Transport of Melphalan by Two Amino Acid Carriers in L5178Y Lymphoblasts in Vitro

Cancer Research , Volume 39 (2 Part 1 ): 353 – Feb 1, 1979

Abstract

Investigation of the mechanism of uptake of melphalan by L5178Y lymphoblasts has been extended with particular emphasis on the chemical specificity of the transport mechanism. Evidence was obtained that uptake of melphalan was an active carrier-mediated process. Uptake appeared to proceed "uphill" against a concentration gradient of approximately eight-fold and was temperature sensitive, partly sodium dependent, and inhibited by ouabain and p -hydroxymercuribenzoate. Drug uptake followed biphasic Michaelis-Menten kinetics suggesting the involvement of at least two carrier systems and was markedly inhibited by a variety of amino acids. Melphalan uptake was strongly inhibited by ß-2-aminobicyclo2,2,1heptane-2-carboxylic acid, a specific inhibitor of the L amino acid transport (leucine-preferring) system but not by 2-aminoisobutyric acid or 2-(methylamino)-isobutyric acid, specific inhibitors of the A amino acid (alanine-preferring) system. Under conditions in which the L and A systems were saturated by ß-2-aminobicyclo-2,2,1heptane-2-carboxylic acid and 2-aminoisobutyric acid, drug uptake was inhibited by serine, an amino acid known to be transported by the ASC (alanine, serine, and cysteine) system. In reciprocal experiments with leucine as substrate, melphalan inhibited uptake of the amino acid by both the L system and a second system resembling ASC. All of the carrier-mediated uptake of melphalan could be accounted for by transport on these two systems. In the drug concentration range of 3.33 to 20 µ M , carriermediated uptake of melphalan appeared to be almost equally divided between the L system and the system resembling ASC, while in the 20 to 100 µ M concentration range, uptake by the L system became increasingly dominant. Uptake of melphalan by the L carrier system had a K m of 8.0 ± 3.0 x 10 -5 M and a V max of 1.1 ± 0.4 x 10 -16 mol/cell/min, while uptake by the second system had a K m of 1.0 ± 0.7 x 10 -5 M and a V max of 2.2 ± 2.4 x 10 -17 mol/cell/min. 1 This work was supported by a grant from the National Cancer Institute of Canada.

Loading next page...
 
/lp/american-association-of-cancer-research/evidence-for-active-transport-of-melphalan-by-two-amino-acid-carriers-VjoHzHTi98

References

References for this paper are not available at this time. We will be adding them shortly, thank you for your patience.

Publisher
American Association of Cancer Research
Copyright
Copyright © 1979 by the American Association for Cancer Research.
ISSN
0008-5472
Publisher site

Abstract

Investigation of the mechanism of uptake of melphalan by L5178Y lymphoblasts has been extended with particular emphasis on the chemical specificity of the transport mechanism. Evidence was obtained that uptake of melphalan was an active carrier-mediated process. Uptake appeared to proceed "uphill" against a concentration gradient of approximately eight-fold and was temperature sensitive, partly sodium dependent, and inhibited by ouabain and p -hydroxymercuribenzoate. Drug uptake followed biphasic Michaelis-Menten kinetics suggesting the involvement of at least two carrier systems and was markedly inhibited by a variety of amino acids. Melphalan uptake was strongly inhibited by ß-2-aminobicyclo2,2,1heptane-2-carboxylic acid, a specific inhibitor of the L amino acid transport (leucine-preferring) system but not by 2-aminoisobutyric acid or 2-(methylamino)-isobutyric acid, specific inhibitors of the A amino acid (alanine-preferring) system. Under conditions in which the L and A systems were saturated by ß-2-aminobicyclo-2,2,1heptane-2-carboxylic acid and 2-aminoisobutyric acid, drug uptake was inhibited by serine, an amino acid known to be transported by the ASC (alanine, serine, and cysteine) system. In reciprocal experiments with leucine as substrate, melphalan inhibited uptake of the amino acid by both the L system and a second system resembling ASC. All of the carrier-mediated uptake of melphalan could be accounted for by transport on these two systems. In the drug concentration range of 3.33 to 20 µ M , carriermediated uptake of melphalan appeared to be almost equally divided between the L system and the system resembling ASC, while in the 20 to 100 µ M concentration range, uptake by the L system became increasingly dominant. Uptake of melphalan by the L carrier system had a K m of 8.0 ± 3.0 x 10 -5 M and a V max of 1.1 ± 0.4 x 10 -16 mol/cell/min, while uptake by the second system had a K m of 1.0 ± 0.7 x 10 -5 M and a V max of 2.2 ± 2.4 x 10 -17 mol/cell/min. 1 This work was supported by a grant from the National Cancer Institute of Canada.

Journal

Cancer ResearchAmerican Association of Cancer Research

Published: Feb 1, 1979

There are no references for this article.