UDP-glucuronosyltransferase in the rat olfactory bulb: Identification of the UGT1A6 isoform and age-related changes in 1-naphthol glucuronidation

Xenobiotic glucuronidation represents a major metabolic protection of the b rain against chemical aggressions at blood-brain interfaces. We previously observed that glucuronidation of l-naphthol was very effective in olfactory bulb, which is a pathway for the entry of foreign molecules into the brain . In this wort;, we showed that l-naphthol glucuronidation varied according to age. It was very high at birth, then decreased markedly in 3-month-old rats and increased again significantly during aging. By Western blot and re verse transcription-polymerase chain reaction (RT-PCR), we demonstrated the presence in the olfactory bulb of the UDP-glucuronosyltransferase (UGT) 1A 6 isoform, which catalyzes the glucuronidation of phenols, such as l-naphth ol. Quantitative RT-PCR indicated that the mRNA levels encoding UGT1A6 did not significantly change according to age, thus suggesting that other diffe rently regulated UGT isoforms were present and would account for the variat ions of l-naphthol glucuronidation observed.