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D2O and the sodium pump in squid nerve membrane
The Journal of Membrane Biology
|January 1, 1987
Summary
Deuterium oxide (D2O) affects sodium-potassium pump function in squid axons, altering ion transport and suggesting conformational changes. Temperature and ATP levels further influence these D2O-induced effects on the Na pump.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Physiology
Background:
- The sodium-potassium pump (Na+/K+-ATPase) is crucial for maintaining cell membrane potential and ion gradients.
- Understanding the molecular mechanisms and environmental influences on Na+/K+-ATPase activity is vital for cellular function.
Purpose of the Study:
- To investigate the effects of deuterium oxide (D2O) on sodium (Na+) efflux in squid axons.
- To explore how D2O interacts with potassium (K+) sensitivity and affinity.
- To elucidate the role of conformational changes in the Na pump complex.
Main Methods:
- Experiments were conducted using squid axons in artificial seawater (ASW) with varying potassium (K+) concentrations.
- Deuterium oxide (D2O) was used to replace normal water (H2O).
- Axons were manipulated by injecting arginine to alter ATP/ADP ratios and temperature was varied.
Main Results:
- D2O significantly reduced Na+ efflux in 10 K ASW but had minimal effect in 0 K ASW.
- D2O decreased K+ sensitivity while increasing K+ affinity for the Na pump.
- A decrease in temperature mimicked D2O's effects.
- Arginine injection, lowering ATP/ADP ratio, resulted in D2O-sensitive efflux in 0 K ASW.
Conclusions:
- D2O induces conformational changes in the Na pump molecular complex, affecting its ion transport properties.
- Temperature and intracellular ATP levels modulate the Na pump's response to D2O.
- These findings provide insights into the allosteric regulation of the Na+/K+-ATPase.