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On the discrepancy between whole-cell and membrane patch mechanosensitivity in Xenopus oocytes
1Physiology and Biophysics, University of Texas Medical Branch, Galveston, TX 77555-0641, USA.
The Journal of Physiology
|February 16, 2000
Summary
Xenopus oocytes lack mechanosensitivity due to excess membrane area buffering tension. Membrane geometry changes, not intrinsic channel properties, may alter cell mechanosensitivity.
Area of Science:
- Cell biology
- Biophysics
Background:
- Mechanosensitive ion channels are crucial for cellular responses to physical stimuli.
- Xenopus oocytes are a model system for studying ion channel function.
Purpose of the Study:
- To investigate the mechanosensitivity of Xenopus oocytes.
- To determine the factors contributing to or preventing mechanosensitivity in these cells.
Main Methods:
- Mechanical stimulation (inflation, aspiration, indentation) of voltage-clamped Xenopus oocytes.
- Membrane capacitance measurements and high-resolution imaging of membrane patches.
- Patch clamp electrophysiology to measure membrane conductance and ion channel activity.
Main Results:
- Xenopus oocytes showed no increase in membrane conductance upon mechanical stimulation until visible damage occurred.
- Excess membrane surface area (at least 5x predicted) was identified, potentially buffering tension.
- Membrane flexing and mechanosensitive channel activation were observed in isolated membrane patches under brief pressure/suction.
Conclusions:
- The absence of mechanosensitivity in intact oocytes is likely due to the buffering capacity of excess membrane area.
- Changes in membrane geometry, influenced by cellular processes or conditions, may alter mechanosensitivity independently of intrinsic channel properties.