IDENTIFICATION OF THE URIDINE-DIPHOSPHATE GLUCURONOSYLTRANSFERASE ISOFORM UGT1A6 IN RAT-BRAIN AND IN PRIMARY CULTURES OF NEURONS AND ASTROCYTES

The expression of a phenol uridine diphosphate glucuronosyltransferase (UGT) was investigated in rat brain homogenate and in primary culture s of astrocytes and neurons, by means of model substrates (l-naphthol and 4-methylumbelliferone) assays, Western blot analysis and reverse t ranscription-polymerase chain reaction (RT-PCR) experiments. Glucuroni dation of these substances occurred in cerebral cell or brain homogena tes, although to different extents. The specific activity was the high est in astrocytes, with values more than 10- and 100-fold those found in neurons or total brain, respectively. Using antibodies able to reco gnize several rat liver UGT isoforms, only one protein with an apparen t molecular mass of 54 kDa was detected in astrocyte and neuron homoge nates and brain microsomes. RT-PCR experiments run with primers specif ically designed for the rat liver UGT1A6 revealed amplificons of the e xpected sizes in accordance with the presence of UGT1A6 mRNA. The nucl eotide sequence of the 330-base pair product was 100% homologous to th at of exon 1 of rat liver isoform UGT1A6. In conclusion, this work all owed us to identify for the first time a constitutive cerebral UGT iso form identical to rat liver UGT1AG, which glucuronidates planar phenol ic substances in cultured astrocytes, neurons, and the entire brain. ( C) 1998 Academic Press.