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Updated: Oct 9, 2026
Measurement of Maximum Isometric Force Generated by Permeabilized Skeletal Muscle Fibers
Published on: June 16, 2015
Molecular size-dependent leakage of intracellular molecules from frog skeletal muscle fibers permeabilized with
1Department of Physiology, Jikei University School of Medicine, Tokyo, Japan.
Abstract:
The permeability of beta-escin-treated cell membrane was characterized in terms of the permeant molecular size, by monitoring the leak of cytoplasmic molecules in frog skeletal muscle fibers. With a low concentration of beta-escin (5 microM), most of the cellular ATP was lost within 30-40 min (as revealed by rigor force generation), whereas a fluorescence-labeled dextran injected into the cytoplasm (approximately 10 kDa) and cytoplasmic proteins (14-80 kDa) slowly leaked out of the cell. A high concentration of beta-escin (50-100 microM) accelerated the leak of large molecules. Therefore, low concentrations of beta-escin may be used as a means of permeabilizing the cell membrane to relatively small molecules, while retaining a major fraction of the cellular macromolecules.
Insights
Beta-escin permeabilizes cell membranes, allowing small molecules like ATP to leak out. Low beta-escin concentrations enable selective permeabilization, retaining larger cellular macromolecules.
Area of Science:
- Cell biology
- Biophysics
Background:
- Cell membrane permeability is crucial for cellular function.
- Understanding how substances cross the cell membrane is key to drug delivery and research.
Purpose of the Study:
- To characterize the effect of beta-escin on cell membrane permeability.
- To determine the relationship between beta-escin concentration and molecular size of leaked cytoplasmic molecules.
Main Methods:
- Frog skeletal muscle fibers were treated with varying concentrations of beta-escin.
- Cytoplasmic molecule leakage (ATP, dextran, proteins) was monitored.
- Rigor force generation was used to assess ATP loss.
Main Results:
- Low beta-escin concentrations (5 microM) caused rapid ATP loss but slow leakage of larger molecules (10-80 kDa).
- High beta-escin concentrations (50-100 microM) accelerated the leakage of larger molecules.
- Selective permeabilization was observed, differentiating between small and large molecules.
Conclusions:
- Beta-escin can be used to selectively permeabilize cell membranes.
- Low concentrations of beta-escin allow passage of small molecules while preserving macromolecules.
- This technique has potential applications in cellular research and targeted delivery.
