6.1. Cadmium,oxidativestressandhumandiseaseThe routes of cadmium intake involve the lungs, intestines and skin. Cadmium in the body is predominantly bound to metalloth- ioneins (Hamer, 1986). The cadmium–metallothionein complex is distributed to various tissues and organs and is ultimately reab- sorbed in kidney tubuli (Ohta and Cherian, 1991). There is no mechanism for the excretion of cadmium in humans, thus cad- mium accumulates in tissues. The half-life of cadmium in kidney cortex is 20–35 years. In humans, the largest amount of cadmium is deposited in the kidneys, liver, pancreas and lungs.Cadmium itself is unable to generate free radicals directly, however, indirect formation of ROS and RNS involving the super- oxide radical, hydroxyl radical and nitric oxide has been reported (Waisberg et al., 2003). Some experiments also confirmed the gen- eration of non-radical hydrogen peroxide which itself in turn may be a significant source of radicals via Fenton chemistry (Elinder et al., 1976). Cadmium can activate cellular protein kinases (pro- tein kinase C) which result in enhanced phosphorylation of various transcription factors which in turn lead to activation of target gene expression.
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