Mikroszómás

Mikroszómás, or microsomal, refers to a subcellular fraction consisting of vesicular fragments of the endoplasmic reticulum obtained from disrupted cells by differential centrifugation. It is most commonly prepared from liver tissue but can be isolated from other tissues as well. After homogenization, low-speed spins remove nuclei and cell debris, while ultracentrifugation around 100,000 g yields the microsomal pellet. The resulting preparation is typically resuspended in an appropriate buffer and used for in vitro assays.

The microsomal fraction is enriched with membrane-bound enzymes of the endoplasmic reticulum. The most notable group is the cytochrome P450 family of monooxygenases, along with associated redox partners such as NADPH-cytochrome P450 reductase. Microsomes also contain other phase I and phase II drug-metabolizing enzymes, such as various transferases and hydrolases, as well as lipids that form part of the ER membrane. The presence and activity of these enzymes make microsomes a key tool for studying metabolic processes.

Uses of mikroszómás include exploring in vitro drug metabolism, assessing enzyme kinetics, and evaluating potential drug–drug interactions or enzyme induction and inhibition. They are employed to estimate metabolic stability, biotransformation pathways, and to reconstitute enzymatic systems for research and screening purposes. Microsomal assays are often preferred for hepatic metabolism studies because they reflect a major portion of phase I oxidative reactions occurring in vivo.

Limitations include that microsomes represent only a portion of cellular metabolism, mainly membrane-bound enzymes, and require cofactors such as NADPH. They lack intact cellular architecture and cytosolic enzymes, so results must be extrapolated with caution to whole-organism biology.