1. The major metabolic transformation of orally ingested 14C-DGEBPA is by hydrolytic ring-opening of the two epoxide rings to form diols. This metabolite (the bis-diol of DGEBPA) is excreted in both free and conjugated forms and is further metabolized to various carboxylic acids, including two containing a methylsulphonyl moiety. 2. The product of oxidative dealkylation either of DGEBPA (with concomitant formation of glycidaldehyde) or of the bis-diol of DGEBPA (with concomitant formation of glyceraldehyde) is excreted in both free and conjugated forms in amounts representing 5% of the dose. 3. The high activity of epoxide hydratase towards DGEBPA suggests that glyceraldehyde and not glycidaldehyde is formed in vivo. 4. Hepatic epoxide hydratase activity towards DGEBPA measured in vitro decreased in the order rabbit greater than mouse greater than rat. 5. Two discrete epoxide hydratases are present in large amounts in the mouse. One is membrane-bound in the liver microsomal fraction and the other is a "soluble' enzyme located in the liver cytosol. This cytosolic enzyme was present in only very small amounts in the rat.

1. 14C-DGEBPA dermally applied to mice was only slowly eliminated in the feces (20% dose) and urine (3%), as a mixture of metabolites, over three days. Most of the applied radioactivity (66% dose) was extracted from the application area and its covering foil. 2. When 14C-DGEBPA was given orally to mice it was rapidly excreted; 80% of the administered 14C was eliminated in the feces and 11% in the urine 0-3 days after a single oral dose. 3. The urinary faecal metabolite profiles derived from dermal application and oral dosing were essentially similar.

Ethyl[14C]benzene hydroperoxide administered orally to female rats (30 mg/kg) is rapidly absorbed and metabolized. Most of the administered compound (81%) is eliminated in the 0-24 h urine. Major metabolites include mandelic acid (23%), hippuric acid (34%) and 1-phenylethyl glucuronide (4%). Ethyl[14C]benzene is metabolized via 1-phenylethanol to the same mixture of metabolites as obtained with the hydroperoxide. Biotransformations of the hydroperoxide and their likely biochemical mechanisms are discussed.

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