Developmental changes in hepatic microsomal interactions between UDP-glucuronyltransferase and phospholipid in the rat fetus.

The interaction of hepatic microsomal UDP-glucuronyltransferase (UDPGT) and phospholipid was studied using rat fetuses from the 16th to 21st day of gestation. UDPGT activity for phenol and p-phenylbenzoic acid, and phospholipid content and fluidity increased with day of gestation. Digestion of microsomes with phospholipase A2 removed a similar ratio of phospholipids throughout the gestation days, whereas UDPGT activity decreased with day of gestation, indicating that UDPGT and phospholipids interacted strongly with day of gestation. Use of various modifiers showed a prominent decrease of UDPGT activity in the later part of gestation with changes in tryptophane residues and amino groups, and no change in activity with modification of thiol groups. These results suggest that tryptophane residues and amino groups interact with phospholipids. The results of this work will be useful in analyzing fetotoxicity associating with glucuronidation.