Glucuronic acid toxicity

For example, it is to be noted that UDP-glucuronic acid which is formed in the tissues, is used not only for polysaccharide synthesis, but also for neutralization and removal of toxic and useless materials or foreign compounds from the organism. 

Deconjugation and dehydroxylation reactions occur in the colon, leading to the formation of dozens of new distinct BAs, by the action of the colonic bacteria. The final products enter the enterohepatic circulation and reach the liver where they are reconjugated mostly to either glycine or taurine. Some lithocholic acid, the most toxic substance produced in the body and a known carcinogen, enters the liver where it is sulfated or esterified to glucuronic acid and excreted. 

Koalas Phascolarctos cinereus) increase their glucose intake by 20% if they eat Eucalyptus spp. foliage, which requires conjugation reactions with glucuronic acid for excretion (Eberhard etal, 1975). Goats and sheep eat more of a toxic diet if given surplus food, which helps detoxication (Provenza, 2004). 

Biological systems possess a number of mechanisms for protection against toxic foreign compounds, some of which have already been mentioned. Thus, metabolic transformation to more polar metabolites, which are readily excreted, is one method of detoxication. For example, conjugation of paracetamol with glucuronic acid and sulfate facilitates elimination of the drug from the body and diverts the compound away from potentially toxic pathways (see chap. 7). Alternatively, a reactive metabolite may be converted into a stable metabolite. For example, reactive epoxides can be metabolized by epoxide hydrolase to stable dihydrodiols. 

Many Anabolic/Androgenic Steroids (AAS) are available in an oral form. Unfortunately some are also quite toxic to the liver. Orally administered AAS are very susceptible to first pass liver deactivation unless chemical molecular structures are altered to make them harder to deactivate. When an oral AAS is swallowed it enters the stomach where it is partially broken down and passed to the small intestines. The small intestines contain a group of enzymes called CYP-450 s. These enzymes begin to break down the AAS further in an attempt to deactivate it. The AAS is then absorbed through intestinal mucosa cells and transferred to the liver portal vein for further deactivation into inactive chemicals such as etiocholanone. These chemicals are then conjugated with glucuronic acid and excreted in urine. Up to 100% of the original compound can be deactivated in this process which is known as first pass deactivation. 

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