Cadmium toxicity history, metallothionein protection history, and their problems

<p>Cadmium (Cd), a harmful metal, causes the damages in the kidney, liver, bone, respiratory and circulatory. In particular, chronic renal toxicity, whose main symptom is renal tubular dysfunction, is subject to the safety evaluation of Cd. The chronic renal toxicity occurred in many Cd-polluted areas of Japan. The itai-itai disease, whose main symptoms are renal toxicity and osteomalacia, has occurred in elderly multiparous women as a result of long-term oral intake of Cd due to environmental pollution of Cd in the Jinzu River area in Toyama. With the itai-itai disease as an opportunity, the evaluation of health risk of Cd has been studied, and further research has been carried out to elucidate the mechanism of Cd toxicity. Recently, Cd poisoning due to industrial workplaces and environmental pollution has hardly occurred in Japan. However, the health effects of long-term exposure to trace amounts of Cd have become a problem for the elderly, since Cd is taken into the body through foods such as rice over the course of a lifetime, and its persistence in the body is high. On the other hand, metallothionein (MT) was isolated as a Cd-binding protein from the renal cortex of horses in 1957. Since MT contains a large amount of cysteine, it has a high affinity for metals and has a free radical scavenging effect. Previous studies have clarified that MT is involved in the maintenance of homeostasis of essential metals such as copper and zinc, and plays a protective role against the toxicity of various harmful factors such as Cd and various diseases caused by oxidative stress. In this symposium, it will be introduced the findings on the toxicity of Cd and the biological defense of MT, and also referred to future issues.</p>