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Sodium concentrations affect metabolite uptake and cellular metabolism.
Journal of Cellular Physiology
|May 1, 1978
Summary
Increasing sodium concentrations (Na+) alter nutrient uptake in chick embryo cells by affecting transport kinetics, not cell growth. These changes in deoxyglucose and leucine uptake are independent of protein or RNA synthesis.
Area of Science:
- Cell Biology
- Biochemistry
- Physiology
Background:
- Cellular nutrient uptake is crucial for cell function and survival.
- Extracellular ion concentrations, particularly sodium (Na+), can influence cellular processes.
- Understanding how Na+ affects nutrient transport is key to cell physiology.
Purpose of the Study:
- To investigate the effect of varying extracellular sodium concentrations ([Na+]) on the uptake of glucose, galactose, and leucine in chick embryo cells.
- To determine if Na+ affects nucleoside uptake or cell growth.
- To elucidate the kinetic parameters (Km and Vmax) influenced by [Na+].
Main Methods:
- Chick embryo cells were exposed to a range of Na+ concentrations (100-200 mM).
- Uptake rates of radiolabeled glucose (3H-2-deoxy-D-glucose), galactose, and leucine were measured.
- Kinetic analysis (Km and Vmax) was performed to understand the mechanism of Na+ effect.
- Effects on nucleoside uptake, DNA/RNA synthesis, and cell growth were assessed.
Main Results:
- Increased [Na+] significantly altered the uptake of deoxyglucose and leucine, primarily by changing the Km, while Vmax remained constant.
- Nucleoside uptake was unaffected by [Na+] within the tested range.
- Prior cell exposure to altered [Na+] was necessary for the uptake changes.
- Inhibition of protein or RNA synthesis did not prevent these Na+-induced uptake modifications.
- Slight increases in chick embryo cell growth were observed with higher [Na+], but not in rat NRK cells.
- Similar Na+-dependent uptake changes were observed in mammalian (rat NRK) cells.
Conclusions:
- Extracellular Na+ concentration directly modulates the kinetics of specific nutrient transporters (glucose, leucine) in chick embryo cells.
- The Na+ effect on nutrient uptake is a rapid process, independent of new protein or RNA synthesis.
- These findings highlight a direct role for Na+ in regulating cellular metabolism beyond its electrochemical gradient.
- The observed effects are conserved across different cell types, suggesting a fundamental regulatory mechanism.