RNA/DNA ratios as a sublethal endpoint for large scale toxicity testing with the nematode Caenorhabditis elegans.
Udu Ibiam and Alastair Grant, 2005.
Environmental Toxicology and Chemistry 24(5)1155-1159
RNA/DNA ratios as a sublethal endpoint for large scale toxicity testing with the nematode Caenorhabditis elegans.Udu Ibiam and Alastair Grant, 2005.Environmental Toxicology and Chemistry 24(5)1155-1159 |
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Caenorhabditis elegans is increasingly attractive as a toxicity test organism, particularly as a model system to study mechanisms of toxicity at a molecular level and the way that these lead to whole organism and population level effects. Inhibitions of growth, reproduction, movement, and feeding rate have all been proposed as sublethal toxicity endpoints. These endpoints are more sensitive than 24-hour acute toxicity endpoints, but assays are much more time consuming, making them difficult to use in mass screening. RNA/DNA ratio, after 48-hour exposure to metals has EC50 values of 0.05, 0.6, 6.1 and 35 mg/L for Cu, Pb, Cd and Zn, respectively. This makes it a slightly more sensitive toxicity endpoint than reduction of individual growth after 72-hour exposure to the same concentrations. This facilitates the near-simultaneous assessment of sublethal toxicity in many nematode samples. The constant cell number of C. elegans means that different stages in the life history have very different RNA/DNA ratios even in the absence of toxins. So, RNA/DNA ratios can only be used on pre-reproductive, age synchronised cultures. Assessing the sublethal toxicity of metals to C. elegans shows that it is particularly sensitive to Cu.
This work will be of interest to the wider C. elegans community as well as to environmental toxicologists, as it provides a method for the rapid measurement of growth rates in large numbers of samples. For example, it will enable the assessment of sublethal RNAi phenotypes and high throughput screening of sublethal effects of pharmaceuticals and other compounds. Reprints are available on request from Alastair Grant.
Dr Alastair Grant
Director
Centre for Ecology,
Evolution and Conservation
School of
Environmental Sciences
University of
East Anglia
Norwich
NR4 7TJ
UK
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