Determination of 125I-labelled thyroxine glucuronide by reversed-phase high-performance liquid chromatography using on-line radiochemical detection to determine UDPglucuronosyltransferase activity.

A convenient, fast and highly sensitive high-performance liquid chromatographic method, using on-line radiochemical detection, is described for the determination of [125I]thyroxine glucuronide. The method involves direct injection of the supernatant, a total analysis time of 30 min and a detection limit of 1 pmol. The results demonstrate that the method is suitable for the determination of UDPglucuronosyltransferase activity with thyroxine as substrate in native hepatic microsomes.