Example 101

Carbon tetrachloride, widely used as a solvent, has been implicated in liver damage. The primary effect is accumulation of fatty deposits within liver cells followed by cellular necrosis. Various elements of the cells are damaged by carbon tetrachloride. Although the exact mechanisms are unclear, it appears that a reactive metabolite of carbon tetrachloride attacks cellular macromolecules, interfering with cellular function and potentially resulting in cell death. Other halogenated alkanes and alkenes (e.g., PCA, DCA, TCA, TCE) seem to follow similar mechanisms of action, albeit with different levels of response. However, all of these compounds produce reactive metabolites and are thus implicated in varying degrees with car-cinogenesis as well.

Finally, chemicals can block the communication functions of the body. Some chemicals interfere with receptor-ligand interactions. These chemicals frequently target the nervous or endocrine systems. Chemical contaminants can act as exogenous ligands that interfere with the chemical messaging systems described previously, thereby disrupting the normal pattern of chemical communication within the body. Other chemicals can disrupt physiological communication systems by interfering with excitable membranes. The effect of DDT on the nervous system (by blocking open a sodium gate on the axonal membrane, thus degrading the ability of the cell to achieve a normal resting state) is a prime example. Interference with calcium metabolism can also lead to disruption of intercellular communication, as calcium frequently serves as a second messenger in the regulation of intracellular functions.

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