Microsome Preparation Protocol

The inside of a cell is enormously complex. Besides the nucleus, there is a mass of membranes -- endoplasmic reticulum -- that handles all metabolic functions. Scientists found that opening the cells produced microsomes -- small vesicles made of the endoplasmic reticulum.

Methods

• Scientists use a variety of methods to break open cells: sonicators, freeze-thaw cycles, homogenizers, detergents and for the larger samples, blenders. They centrifuge this slurry at slow speed to pellet the bigger pieces -- nuclei and unbroken cells -- and this pellet is discarded. The remaining suspension is centrifuged at high speed to pellet the microsomes -- these are resuspended in a buffer for use.

Considerations

• The scientist should consider a number of points before starting. First would be the cell type -- for instance liver should be perfused to remove contaminating blood. Second, molecules to be studied may require a particular temperature for stability. Third, the microsomes can be separated into different sizes, therefore the centrifuge speed can be critical for obtaining the desired fraction.

Uses

• Drug metabolism can be studied in microsomes.

  Researchers use microsomes to identify and define metabolic pathways characteristic to different cell types. However, because the liver is the metabolic site in animals, scientists -- particularly in the pharmaceutical industry -- use liver microsomes to look at drug metabolism.