Defense mechanisms of normal and tumor cells.

This paper reviews the protective systems of normal and tumor cells against chemical and radiation injury. The glutathione redox cycle is an important cell defense system that can be compromised by various chemical modifiers. Acute cell injury can involve the glutathione pools of both the cytosol and the mitochondria. Intracellular calcium may have a role in cell death following acute cell injury but extracellular calcium does not seem to initiate the events leading to cell death. Changes in the glutathione redox status affects the distribution of intracellular calcium and the protein thiol-disulfide redox status. Formation of glutathione protein-mixed disulfides is discussed in terms of a possible protective mechanism against oxidative injury.