UDP-glucuronyl transferase enzyme family in both human and Balb/c mouse lung.

endogenous and xenobiotic compounds. The UDPglucuronyl transferase (UGT) enzyme family catalysing glucuronidation is located in endoplasmic reticulum and expressed predominantly in the liver. This enzyme family has been identified in extrahepatic tissue, including lung tissue, for some time [l]. UGT enzyme activity has also been described in human fetal liver tissue to both planar phenol compounds and more complex structures such as bilirubin and steroid hormones [2]. We have previously shown the presence of another endoplasmic reticulum enzyme, normally associated with the liver, glucose-6-phosphatase (G6P), in the fetal tracheobronchial system. This enzyme first appears in the fetal tracheal epithelial just prior to the appearance of terminally differentiated epithelial cells [3]. We decided, therefore, to look and see if the UGT family of enzymes was expressed in developing fetal lung and to compare its spatial and temporal expression with that of G6P. Access to human lung tissue is very limited making a study of developmental changes in UGT activity difficult. The Balb/c mouse was, therefore, used as a model to study the ontogeny of UGT activity in lung tissue.