S9 fraction

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The S9 fraction is the product of an organ tissue homogenate used in biological assays. The S9 fraction is most frequently used in assays that measure the metabolism of drugs and other xenobiotics. It is defined by the U.S. National Library of Medicine's "IUPAC Glossary of Terms Used in Toxicology" [1] as the "Supernatant fraction obtained from an organ (usually liver) homogenate by centrifuging at 9000 g for 20 minutes in a suitable medium; this fraction contains cytosol and microsomes." The microsomes component of the S9 fraction contain cytochrome P450 isoforms (phase I metabolism) and other enzyme activities. The cytosolic portion contains the major part of the activities of transferases (phase II metabolism). [2] The S9 fraction is easier to prepare than purified microsomes. [3]

Contents

Applications

The S9 fraction has been used in conjunction with the Ames test [4] to assess the mutagenic potential of chemical compounds. [5] Chemical substances sometimes require metabolic activation in order to become mutagenic. Furthermore, the metabolic enzymes of bacteria used in the Ames test differ substantially from those in mammals. Therefore, to mimic the metabolism of test substance that would occur in mammals, the S9 fraction is often added to the Ames test.

The S9 fraction has also been used to assess the metabolic stability of candidate drugs. [6]

Related Research Articles

Ames test

The Ames test is a widely employed method that uses bacteria to test whether a given chemical can cause mutations in the DNA of the test organism. More formally, it is a biological assay to assess the mutagenic potential of chemical compounds. A positive test indicates that the chemical is mutagenic and therefore may act as a carcinogen, because cancer is often linked to mutation. The test serves as a quick and convenient assay to estimate the carcinogenic potential of a compound because standard carcinogen assays on mice and rats are time-consuming and expensive. However, false-positives and false-negatives are known.

<i>In vitro</i> Latin term meaning outside a natural biological environment

In vitro studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology and its subdisciplines are traditionally done in labware such as test tubes, flasks, Petri dishes, and microtiter plates. Studies conducted using components of an organism that have been isolated from their usual biological surroundings permit a more detailed or more convenient analysis than can be done with whole organisms; however, results obtained from in vitro experiments may not fully or accurately predict the effects on a whole organism. In contrast to in vitro experiments, in vivo studies are those conducted in living organisms, including humans, and whole plants.

Mutagen

In genetics, a mutagen is a physical or chemical agent that permanently changes genetic material, usually DNA, in an organism and thus increases the frequency of mutations above the natural background level. As many mutations can cause cancer, such mutagens are therefore carcinogens, although not all necessarily are. All mutagens have characteristic mutational signatures with some chemicals becoming mutagenic through cellular processes. Not all mutations are caused by mutagens: so-called "spontaneous mutations" occur due to spontaneous hydrolysis, errors in DNA replication, repair and recombination.

Pharmacology branch of biology concerning drugs

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Ethidium bromide DNA gel stain and veterinary drug

Ethidium bromide is an intercalating agent commonly used as a fluorescent tag in molecular biology laboratories for techniques such as agarose gel electrophoresis. It is commonly abbreviated as EtBr, which is also an abbreviation for bromoethane. To avoid confusion, some laboratories have used the abbreviation EthBr for this salt. When exposed to ultraviolet light, it will fluoresce with an orange colour, intensifying almost 20-fold after binding to DNA. Under the name homidium, it has been commonly used since the 1950s in veterinary medicine to treat trypanosomiasis in cattle. The high incidence of antimicrobial resistance makes this treatment impractical in some areas, where the related isometamidium chloride is used instead. Ethidium bromide may be a mutagen, although this depends on the organism exposed and the circumstances of exposure.

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Earl Wilbur Sutherland Jr.

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In cell biology, microsomes are heterogenous vesicle-like artifacts re-formed from pieces of the endoplasmic reticulum (ER) when eukaryotic cells are broken-up in the laboratory; microsomes are not present in healthy, living cells.

Methylcholanthrene Chemical compound

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CYP3A4

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Sudan I Chemical compound

Sudan I, is an organic compound, typically classified as an azo dye. It is an intensely orange-red solid that is added to colourise waxes, oils, petrol, solvents, and polishes. Sudan I has also been adopted for colouring various foodstuffs, especially curry powder and chili powder, although the use of Sudan I in foods is now banned in many countries, because Sudan I, Sudan III, and Sudan IV have been classified as category 3 carcinogens by the International Agency for Research on Cancer. Sudan I is still used in some orange-coloured smoke formulations and as a colouring for cotton refuse used in chemistry experiments.

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CYP2C9

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6
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CH
2
. It is related to bisphenol A through its basic structure, as both belong to the category of molecules known as bisphenols, which feature two phenol groups connected via a linking group. In BPF, the two aromatic rings are linked by a methylene connecting group.

EG-018

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References

  1. Duffus JH, Nordberg M, Templeton DM (2007). "Glossary of Terms Used in Toxicology, 2nd Edition". Pure Appl Chem. 79 (7): 1153–1344. doi: 10.1351/pac200779071153 .
  2. Greim, Helmut; Snyder, Robert (2008). Toxicology and risk assessment: a comprehensive introduction. Wiley-Interscience. p. 387. ISBN   978-0-470-86893-5.
  3. Vogel, H. Gerhard (2006). Drug discovery and evaluation: safety and pharmacokinetic assays. Springer. p. 509. ISBN   3-540-25638-5.
  4. Mortelmans K, Zeiger E (November 2000). "The Ames Salmonella/microsome mutagenicity assay". Mutat. Res. 455 (1–2): 29–60. doi:10.1016/S0027-5107(00)00064-6. PMID   11113466.
  5. Sakura, Atsushi; Suzuki, Satoshi; Satoh, Tetsuo (2004). "Improvement of the Ames test using human liver S9 preparation". In Yan, Zhengyin; Caldwell, Gary (eds.). Optimization in drug discovery: in vitro methods. Methods in pharmacology and toxicology. Humana Press. pp. 325–336. ISBN   1-58829-332-7.
  6. Wu W-N, McKown LA (2004). "Chapter 11: In Vitro Drug Metabolite Profiling Using Hepatic S9 and Human Liver Microsomes". In Yan Z, Cadwell GW (eds.). Optimization in Drug Discovery: In Vitro Methods (Methods in Pharmacology and Toxicology). Totowa, NJ: Humana Press. pp. 163–184. doi:10.1385/1-59259-800-5:163. ISBN   1-58829-332-7.

Further reading

This article incorporates text from the United States National Library of Medicine, which is in the public domain.