ABSTRACT
Many toxic substances are known to cause poisoning through a chain of events that begins with action at a very specic target. Often, this target is a biological molecule with which the toxicant binds or reacts, such as one or more of the various types of proteins, lipids, and nucleic acids within the cell. Symptoms resulting from exposure to a toxicant may relate directly to this molecular event, or may be complicated by secondary effects, just as symptoms of a disease may be due to physiological imbalances that are secondary to the initial infection. Therefore, identication of the primary site of action requires careful collection and interpretation of biochemical and physiological evidence. For some toxicants, this initial event in poisoning, or molecular lesion, has been characterized. For many other toxicants, the precise interaction of the toxicant with one or more specic biological molecules has yet to be demonstrated. With the increasingly powerful experimental techniques available, however, it is likely that precise molecular sites of action will be described for many more toxicants in the near future.
