10.1. Mechanism of Toxic Compounds Detoxification
Xenobiotics are compounds that have no nutrient value (cannot be used for energy needs by the body) and potentially toxic. They are present as natural components of foods or they may be introduced into foods as additives or through processing. Pharmacologic and recreational drugs are also xenobiotic compounds.
The liver is the principal organ in the body for the degradation of these compounds. Potentially toxic agents absorbed from the gut or delivered to the liver by the hepatic artery: NH3, products of amino acid putrefaction in the intestine, peptide and steroid hormones, catecholamines, and heme degradation products. Pharmacological agents performed their functions have to be removed from the body in invariable or modified form. Within the liver, these compounds are properly metabolized, as well as potentially harmful substances are detoxified and prepared for subsequent excretion into the urine or feces. Among other functions, the liver is equipped with a broad spectrum of detoxifying mechanisms. The sequential transport steps carried out by such as endosomes, mitochondria, lysosomes, as well as the nucleus include (1) uptake, (2) intracellular binding and sequestration, (3) metabolism, (4) sinusoidal secretion, and (5) biliary excretion. The rate of hepatobiliary transport is determined, in part, by the rate of activity of each of these steps.
Detoxification stages are divided into two phases. Because many of xenobiotics are lipophilic, they are oxidized, hydroxylated, or hydrolyzed by enzymes in phase I reactions. Phase I reactions introduce or expose hydroxyl groups or other reactive sites that can be used for conjugation reactions (the phase II reactions).