Factors Affecting Toxic Responses Metabolism

As discussed in the preceding chapter, foreign and potentially toxic compounds absorbed into biological systems are generally lipophilic substances. They are therefore not ideally suited to excretion, as they will be reabsorbed in the kidney or from the gastrointestinal tract after biliary excretion. For example, highly lipophilic substances such as polybrominated biphenyls and DDT are poorly excreted and therefore may remain in the animal s body for years. 

In the biotransformation of foreign compounds, the body attempts to convert such lipophilic substances into more polar, and consequently, more readily excreted metabolites. 

The exposure of the body to the compound is hence reduced and potential toxicity decreased. This process of biotransformation is therefore a crucial aspect of the disposition of a toxic compound in vivo. Furthermore, as will become apparent later in the book, biotransformation may also underlie the toxicity of a compound. 

The metabolic fate of a compound can therefore have an important bearing on its toxic potential, disposition in the body, and eventual excretion. 

The parent molecule is transformed into a more polar metabolite, often by the addition of ionizable groups. 

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CHAPTER 4 FACTORS AFFECTING TOXIC RESPONSES METABOLISM 65... 

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