Chemical toxicity of thorium in Saccharomyces cerevisiae

Thorium (232Th), an actinoide element, is among the most common and naturally occurring radioactive materials distributed in our environment. Thorium has been used as a radiographic contrast agent (thorotrast) from 1930 to 1955, and many studies on its effects to the human body have been reported. Once thorium is injected in the body, the risk of cancer is increased by the direct bombardment from alpha-particle with high linear energy transfer during decay of Thorium. However, these many reports focus on the irradiation damage by long-term exposure of thorium. The acute toxicity of thorium is greater risk from the chemical toxicity than from the radiological toxicity. Here, we evaluated the effect of thorium from the stand point of chemical toxicity using yeast DNA microarray. In this experiment, genes that contribute to “C-compound and carbohydrate metabolism”, “energy”, and “cell rescue, defense and virulence” were significantly induced. These genes were classified into oxidative stress, glycogen and trehalose metabolism, sugar transport, and cell wall damage. On the contrary, only one gene related to DNA damage was detected. These results indicate that thorium causes the damage of cell wall and induces the oxidative stress. In order to overcome oxidative stress, yeast cells promote the glycogen and trehalose metabolisms and shift to anaerobic fermentation. Keywords: stress response Series containes 3 hybridization results from independent biological samples, and each experiment have high and low power scanned data respectively.