Induction of system A amino acid transport through long-term treatment with ouabain: Correlation with increased (Na+/K+)-ATpase activity
✍ Scribed by Mark A. Schenerman; Kirk J. Leister; David K. Trachtenberg; Efraim Racker
- Publisher
- John Wiley and Sons
- Year
- 1988
- Tongue
- English
- Weight
- 588 KB
- Volume
- 135
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Mouse embryo fibroblast cells (C3H-1 0Tll2) and the methylcholanthrenetransformed derivative (MCA-1 OT1/2) were treated with basal modified Eagle's medium (BME) containing 10% fetal bovine serum and varying concentrations of ouabain ranging from 0.05 m M to 0.7 m M 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-' . min-l in the C3H-l0TIl2 cells and from approximately 300 to 700 pmol AIB accumulated . mg protein-' . min-' in the MCA-1 OT1/Z cells. The (Na+/K+)-ATPase pump activity also increased from approximately 12 to 46 nmol Rb+ accumulated . mg protein-' . min-' in the normal cells and from approximately 20 to 42 nmol Rbt accumulated . mg protein-' . min-' in the transformed cells. System A and the (Na+/K+)ATPase activity were maximally increased at approximately 0.4-0.6 m M ouabain in the normal cells in contrast to the transformed cells which were maximally stimulated at a concentration of approximately 0.2 m M ouabain. This treatment with ouabain increased the [Naf],/[K'], as measured by atomic absorption spectroscopy, and thereby decreased the N a t 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 ouabaininduced 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.