Induction of system A amino acid transport through long-term treatment with ouabain: correlation with increased (Na+/K+)-ATPase activity

• Published in: Journal of cellular physiology Vol. 135; no. 2; p. 157
• Main Authors: Schenerman, M A, Leister, K J, Trachtenberg, D K, Racker, E
• Format: Journal Article
• Language: English
• Published: United States 01.05.1988
• Subjects: Amino Acids - metabolism; Aminoisobutyric Acids - metabolism; Animals; Biological Transport - drug effects; Cells, Cultured; Kinetics; Mice; Ouabain - pharmacology; Potassium - metabolism; Rubidium - metabolism; Sodium - metabolism; Sodium-Potassium-Exchanging ATPase - metabolism
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041350202

Mouse embryo fibroblast cells (C3H-10T1/2) and the methylcholanthrene-transformed derivative (MCA-10T1/2) were treated with basal modified Eagle's medium (BME) containing 10% fetal bovine serum and varying concentrations of ouabain ranging from 0.05 mM to 0.7 mM for 16 h in culture. After replacing the ouabain-containing medium with Earl's balanced salts solution, System A amino acid transport activity increased from approximately 40 to 500 pmol AIB accumulated.mg protein-1.min-1 in the C3H-10T1/2 cells and from approximately 300 to 700 pmol AIB accumulated.mg protein-1.min-1 in the MCA-10T1/2 cells. The (Na+/K+)-ATPase pump activity also increased from approximately 12 to 46 nmol Rb+ accumulated.mg protein-1.min-1 in the normal cells and from approximately 20 to 42 nmol Rb+ accumulated.mg protein-1.min-1 in the transformed cells. System A and the (Na+/K+)ATPase activity were maximally increased at approximately 0.4-0.6 mM ouabain in the normal cells in contrast to the transformed cells which were maximally stimulated at a concentration of approximately 0.2 mM ouabain. This treatment with ouabain increased the [Na+]i/[K+]i as measured by atomic absorption spectroscopy, and thereby decreased the Na+ and K+ electrochemical gradients. Our data show that the internal ion gradients inverted at a lower concentration of ouabain in the transformed cells compared to the normal cells. The ouabain-induced increase in pump and System A activity shown here was used as a tool to further investigate the coordinated ion transport regulation in the control of cell growth.