Modeling of Cellular Arginine Uptake by More Than One Transporter

• Published in: The Journal of membrane biology Vol. 245; no. 1; pp. 1 - 13
• Main Authors: Nel, Marietha J., Woodiwiss, Angela J., Candy, Geoffrey P.
• Format: Journal Article
• Language: English
• Published: New York Springer-Verlag 2012; Springer Nature B.V
• Subjects: Algorithms; Amino Acid Transport Systems - antagonists & inhibitors; Amino Acid Transport Systems - metabolism; Arginine - metabolism; Biochemistry; Biomedical and Life Sciences; Carboxylic Acids - pharmacology; Cells, Cultured; Ethylmaleimide - pharmacology; Human Physiology; Human Umbilical Vein Endothelial Cells - metabolism; Humans; Kinetics; Leucine - pharmacology; Life Sciences; Membrane Transport Proteins - metabolism; Models, Biological; Nonlinear Dynamics; Regression Analysis; Sodium - chemistry; Endothelial cell; Amino acid transport; Kinetics
• ISSN: 0022-2631; 1432-1424
• DOI: 10.1007/s00232-011-9408-0

Determining the kinetic constants of arginine uptake by endothelial cells mediated by more than one transporter from linearization of data as Eadie-Hofstee plots or modeling which does not include the concentration of trace radiolabeled amino acid used to measure uptake may not be correct. The initial rate of uptake of trace [
3
H]
l
-arginine by HUVECs and ECV
304
cells in the presence of a range of unlabeled arginine and modifiers was used in nonlinear models to calculate the constants of arginine uptake using GraphPad Prism. Theoretical plots of uptake derived from constants determined from Eadie-Hofstee graphs overestimated uptake, whereas those from the nonlinear modeling approach agreed with experimental data. The contribution of uptake by individual transporters could be modeled and showed that leucine inhibited the individual transporters differently and not necessarily competitively.
N
-Ethylmaleimide inhibited only y
+
transport, and BCH may be a selective inhibitor of y
+
L transport. The absence of sodium reduced arginine uptake by y
+
L transport and reduced the
K
m
′, whereas reducing sodium decreased arginine uptake by y
+
transport without affecting the
K
m
′. The nonlinear modeling approach using raw data avoided the errors inherent in methods deriving constants from the linearization of the uptake processes following Michaelian kinetics. This study provides explanations for discrepancies in the literature and suggests that a nonlinear modeling approach better characterizes the kinetics of amino acid uptake into cells by more than one transporter.