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Influence of dolichol on microsomal membrane functions
F Aberg1, A Jakobsson-Borin, M Olsson
1Department of Biochemistry, Stockholm University, Sweden.
Summary
Rat liver microsomes were treated to remove lipids like dolichol and cholesterol. Reintroducing these lipids restored membrane function, highlighting their roles in membrane fluidity and enzyme activity.
Area of Science:
- Biochemistry
- Cell Biology
- Membrane Biology
Background:
- Microsomal membranes contain essential lipids like dolichol and cholesterol.
- Lipid products of the mevalonate pathway are crucial for membrane integrity and function.
Purpose of the Study:
- To investigate the functional roles of dolichol and cholesterol in rat liver microsomes.
- To assess the impact of lipid removal and reincorporation on membrane permeability and enzyme activity.
Main Methods:
- Rat liver microsomes were extracted with n-pentane to remove specific lipids.
- Lipids (dolichol, cholesterol) were reincorporated into extracted membranes.
- Electron microscopy and permeability assays were used to evaluate membrane structure and function.
- Microsomal enzyme activities were measured after lipid reincorporation.
Main Results:
- Extraction did not disrupt vesicular membrane structure but altered permeability, especially for charged molecules.
- Extracted vesicles showed increased contraction with non-penetrating compounds, which was reversed by dolichol or cholesterol reincorporation.
- Dolichol and cholesterol affected membrane fluidity, with cholesterol significantly modifying certain enzyme activities.
Conclusions:
- n-pentane extraction and lipid reincorporation is a valid method to study lipid function in microsomes.
- Dolichol and cholesterol play distinct roles in modulating microsomal membrane properties and enzyme functions.
- Cholesterol has a more pronounced effect on integral microsomal membrane enzyme activities than dolichol.