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Cytoplasmic calcium buffer capacity determined with Nitr-5 and DM-nitrophen
N F al-Baldawi1, R F Abercrombie
1Department of Physiology, Emory University School of Medicine, Atlanta, Georgia, USA.
Cell Calcium
|June 1, 1995
Summary
Intracellular calcium buffering in Myxicola infundibulum giant axons relies on organelles and MgATP. Removing these components impairs calcium recovery after release, affecting buffer capacity.
Area of Science:
- Cellular Physiology
- Neuroscience
- Biochemistry
Background:
- Intracellular calcium ([Ca2+]) regulation is crucial for neuronal function.
- The giant axon of Myxicola infundibulum provides a model for studying axonal physiology.
- Understanding calcium buffering mechanisms is key to comprehending cellular responses.
Purpose of the Study:
- To investigate the intracellular calcium buffer capacity in Myxicola infundibulum giant axon cytoplasm.
- To determine the role of organelles and MgATP in calcium buffering.
- To assess the impact of pH and basal calcium levels on buffer capacity.
Main Methods:
- Photolytic release of calcium from caged compounds.
- Monitoring free calcium ([Ca2+]) using Ca-sensing electrodes.
- Experimentation with intact and organelle-depleted cytoplasm.
- Assessment of MgATP and pH effects on calcium dynamics.
Main Results:
- Cytoplasm with intact organelles showed an initial [Ca2+] spike followed by recovery.
- Removal of MgATP reduced both the spike amplitude and recovery.
- Organelle removal abolished the recovery phase, resulting in a step-like [Ca2+] change.
- Buffer capacity was reduced at basal free calcium above 3 microM.
- Buffer capacity averaged ~50 without MgATP and ~100 with 1 mM MgATP for [Ca2+] < 3 microM.
Conclusions:
- Organelles and MgATP are essential for effective intracellular calcium buffering and recovery in Myxicola giant axons.
- Buffer capacity is sensitive to high basal calcium concentrations.
- Significant variability in buffer capacity exists between individual giant axons.