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Sodium-sugar coupling stoichiometry in chick intestinal cells
The American Journal of Physiology
|July 1, 1984
Summary
Sodium-dependent sugar transporters use sodium ions to move sugars across cell membranes. Researchers found the transport ratio is 2 sodium ions to 1 sugar molecule when membrane potential is stable.
Area of Science:
- Biochemistry
- Cell Biology
- Membrane Transport
Background:
- Sodium-dependent sugar transport systems are crucial for nutrient uptake.
- Accurate measurement of transport stoichiometry requires stable membrane potential.
Purpose of the Study:
- To accurately determine the Na+:sugar coupling stoichiometry in chicken intestinal cells.
- To investigate the role of membrane potential in sugar transport.
Main Methods:
- Utilized ion gradients (NO-3, K+ plus valinomycin) to control membrane potential.
- Measured Na+ and sugar fluxes under controlled potential conditions.
Main Results:
- Established a stable 2 Na+:1 sugar coupling stoichiometry under controlled membrane potential.
- Observed a 1:1 ratio when membrane potential was not controlled.
- Stoichiometry remained constant across varying Na+ concentrations.
Conclusions:
- The true coupling stoichiometry for chicken intestinal sugar transport is 2 Na+:1 sugar.
- Membrane potential significantly influences observed stoichiometry.
- Na+ dissociation precedes sugar dissociation from the carrier at the inward-facing membrane.