Metabolism of the epoxy resin component 2,2-bis[4-(2,3-epoxypropoxy)phenyl]propane, the diglycidyl ether of bisphenol a (DGEBPA) in the mouse.; Part II. Identification of metabolites in urine and faeces following a single oral dose of ¹⁴C-DGEBPA

Abstract

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>mouse>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.