Cell culture cellular toxicity

The use of triphenylethylene SERMs as Pgp inhibitors for clinical application has been hampered by unacceptable toxicity at doses required to achieve adequate cellular concentration, which is likely due to the involvement of proteins with the ability to bind these compounds. For instance, toremifene is able to reverse MDR and to sensitize human renal cancer cells to vinblastine in vitro. However, in vivo toremifene is tightly bound to serum proteins, in particular a 1-acid glycoprotein (AAG), which may limit its tissue availability (Braybrooke et al. 2000). In agreement with this, Chatterjee and Harris (1990) have shown that tamoxifen and 4-OH-tamoxifen were similarly potent in reversing MDR in Chinese hamster ovary (CHO) cells with acquired resistance to adriamycin. However, the addition of AAG (0.5 to 2 mg/ml, the range found in vivo) to cell cultures decreased the effect of tamoxifen on reversing MDR, and at the highest AAG concentration there was a complete reversal of the effects of... 

Garrett NE, Lewtas J. 1983. Cellular toxicity in Chinese hamster ovary cell cultures I. Analysis of cytotoxicity endpoints for twenty-nine priority pollutants. Environ Res 32 455-465. 

Lee and Webber studied the toxicity of CR in HeLa cells In culture. In vivo experiments had disclosed only negligible effects on tissue cells, except for the sensory elements of the nervous sys-tern. Lee and Webber,believed that suitable cell cultures might react to compounds of moderate toxicity, thus constituting sensitive tests that would indicate which cellular elements were attacked by compounds like CR. 

Bioassays appeared to fit the bill to perform this service to monitor chemical contamination. They have been around for a while. Until relatively recently, however, they remained in the realm of the laboratory. Only over the last two decades have they found a niche in testing for toxic chemicals in water and sediment, but not yet specifically as a tool for routine water quality monitoring. As Small-scale Freshwater Toxicity Investigations, Volumes 1 and 2 amply demonstrates, the science has now come of age. Assays based on bacteria, microscopic or multi-cellular algae, protozoa, invertebrates and vertebrates (freshwater fish cell cultures) are discussed in... 

A 4.5 ml aliquot of each concentration of the test substance is mixed with a 0.5 ml aliquot of test medium containing any requested organic soil load in lieu of virus and treated as previously described. The cytotoxicity of the cell cultures was scored at the same time as virus-test substance and virus control cultures. Cytotoxicity was graded on the basis of cell viability as determined microscopically. Cellular alterations due to toxicity were graded and reported as toxic (T) if greater than or equal to 50% of the monolayer is affected. 

Although the use of simple test systems to predict genetic effects in whole mammals is desirable, comparison of dosages in submammalian systems with human exposure is extremely complex. The nature of the exposure, cellular toxicity, and units of measurement differ markedly from one type of organism to another. Molecular dosimetry that measures adducts in DNA is promising,1-3 237-239 jjUt the ability to relate exposures in short-term test systems, including mammalian cell cultures, to human risks is primitive. There are much better grounds for qualitative than for quantitative extrapolation. 

Application of fluid-state PC also initiates biochemical changes in cell cultures. Fluid-state PC increases cellular lipid fluidity and decreases the rate of proliferation of HaCaT human keratinocytes. No toxicity was observed.29 Choline, which is a metabolite of PC and the precursor of the organic osmolyte betaine, is actively transported to the keratinocytes. The relevance of this finding is not understood.30 Acetylcholine is synthesized, secreted, and degraded in human keratinocytes.31 In addition, PLD, which generates choline from PC, is involved in the differentiation of keratinocytes.32... 

The most common alteration that cells exhibit upon cultivation in culture is the loss of differentiated function. This is a consequence of the conflicting need to enhance cell proliferation to provide adequate experimental material. Differentiated function of a particular cell type is partly determined by interaction with other cell types and noncellular tissue constituents these are lost upon isolation and traditional cell monoculture. Also, undefined biological materials such as fetal calf serum, pituitary extract, and so on, are routinely added to cell culture because they have been shown empirically to have mitogenic effects, but they also have often unappreciated effects on other cellular functions. With regard to toxicokinetics, one of the most challenging problems is relating effective toxicant concentrations in cell culture to that in vivo (Section 8.7). 

QSAR analysis of studies at the cellular level allows us to get a handle on the physicochemical parameters critical to pharmacokinetics processes, mostly transport. Cell culture systems offer an ideal way to determine the optimum hydrophobicity of a system that is more complex than an isolated receptor. Extensive QSAR have been developed on the toxicity of 3-X-triazinesto many mammalian and bacterial cell lines (202, 209). A comparison of the cytotoxicities of these analogs vs. sensitive murine leukemia cells (L1210/S) and methotrexate-resistant murine leukemia cells (L1210/R) reveals some startling differences. 

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