Mammalian liver cells

Unscheduled DNA Synthesis (UDS) Test with Mammalian Liver Cells In Vivo (Original Guideline, adopted 21 July 1997)... 

Unscheduled DNA synthesis (UDS) test with mammalian liver cells in vivo... 

Multiplicity of Cytochrome P450, Purification, and Reconstitution of Cytochrome P450 Activity. Even before appreciable purification of CYP had been accomplished, it was apparent from indirect evidence that mammalian liver cells contained more than one CYP enzyme. Subsequent direct evidence on the multiplicity of CYPs included the separation and purification of CYP isozymes, distinguished from each other by chromatographic behavior, immunologic specificity, and/or substrate specificity after reconstitution and separation of distinct polypeptides by sodium... 

Propanil is one of a group of amide herbicides (made from aniline treated with organic acids), and is used extensively to control weeds in rice crops. Rice itself contains an enzyme that hydrolyzes propanil to 3,4-dichloroani-line and propionic acid, and so it is resistant to the herbicide. Weeds, lacking this enzyme, are adversely affected by it. (Mammalian liver cells also have an enzyme that causes this hydrolysis.)... 

Test with Mammalian Liver Cells in vivo. 839... 

The principles of this method are the same as and the procedure similar to that for the above described method Unscheduled DNA Synthesis (UDS) Test with Mammalian Liver Cells in vitro . The differences between the in vivo and the in vitro method are related... 

Mitochondria arc membranous organelles (Fig. 1-9) of great importance in the energy metabolism of the cell they are the source of most of the ATP (Chap. 14) and the site of many metabolic reactions. Specifically, they contain the enzymes of the citric acid cycle (Chap. 12) and the electron-transport chain (Chap. 14), which includes the main oxygen-utilizing reaction of the cell. A mammalian liver cell contains about 1.000 of these organelles about 20 percent of the cytoplasmic volume is mitochondrial. 

Clemons, J.H., M. van den Heuvel, J.J. Stegeman, D.G. Dixon and N.C. Bols. Comparison of toxic equivalent factors for selected dioxin and furan congeners derived using fish and mammalian liver cell lines. Can. J. Fish. Aquat. Sci. 51 1577-1584, 1994. 

Purpose. The purpose of the ex vivo unscheduled DNA synthesis (UDS) test on mammalian liver cells is to evaluate the potential of the test substance to induce DNA excision repair in liver cells of treated animals (usually rodents and preferably rats). An increase in UDS activity is indicative of primary DNA damage and subsequent excision repair (Butterworth et al. 1987 Mirsalis and Butterworth 1980 Mirsalis et al. 1982). 

Regulatory Acceptance. The UDS test on mammalian liver cells is weU-validated and widely accepted by regulatory agencies. The optimal expai-mental conditions and rules for data interpretation have been published in OECD guideline 486. 

OECD (1997d). Unscheduled DNA synthesis (UDS) test with mammalian liver cells in vivo. OECD Guideline for Testing of Chemicals 486, 1-8. 

Mitochondrial oxidation of fatty acids is the major source of ATP in mammalian liver cells, and biochemists at one time believed this was true in all cell types. However, rats treated with doflbrate, a drug used to reduce the level of blood lipoproteins, were found to exhibit an increased rate of fatty acid oxidation and a large Increase in the number of peroxisomes in their liver cells. This finding suggested that peroxisomes, as well as mitochondria, can oxidize fatty acids. These small organelles, =0.2-1 pm in diameter, are lined by a single membrane (see Figure 5-21). They are present in all... 

The name cytochrome bs is now generally used for a protohemoprotein which exists in high amounts in the endoplasmic reticulum of mammalian liver cells. It shows an asymmetrical a-absorption band with a peak at 556 nm and a shoulder around 560 nm in the reduced state. However, there has been some confusion about its nomenclature. This cytochrome is firmly bound to the membrane structure and reduced with NADH by a flavoprotein (cytochrome bs reductase) which is also bound to the membrane. It is solubilized by proteolytic cleavage from the membrane and has been crystallized from several sources. The molecular weight of such preparations are about 11,000. Although both primary and ternary structures of such preparations are known, its biological role is still uncertain. Earlier findings have been fully reviewed by Strittmatter (94)-... 

The enzymatic formation of steroid type materials from the open chain epoxy squalenes (Scheme 10.10) are normally accomplished using extract of mammalian liver cells. Although exciting as a synthesis these preparations can only be achieved on very small (mg scale) substrate conversions. Sonochemistry has afforded an inexpensive and convenient alternative... 

Claude, A. Fractionation of mammalian liver cells by differential centrifugation. I. Problems, methods, and preparation of extract. J. exp. Med. 84, 51-59(1946)... 

Epoxide hydrolases have been purified from mammalian liver cells [63-66] but also from microbial sources such as Bacillus megaterium [67], Corynebacterium [45,46,68], Pseudomonas sp. [46,69], and dematiaceous fungi such as Ulocladium atrum and Zopfiella karachiensis [70]. However, some of these enzymes were only partially purified [67,68], or their enantioselectivity was not investigated [69] or was very low [45,46]. More recently, two bacterial epoxide hydrolases with high activity and high enantioselectivity were purified and characterized from Rhodococcus sp. NCIMB 11216 [71] and Nocardia TBl [72]. 

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