Tissue- and Gender-Specific mRNA Expression of UDP-Glucuronosyltransferases (UGTs) in Mice

UDP-glucuronosyltransferases (UGTs) catalyze phase II biotransformation reactions in which lipophilic substrates are conjugated with glucuronic acid to increase water solubility and enhance excretion. Currently, little information regarding tissue- or gender-specific expression of mouse UGTs is available. Mice are increasingly popular models in biomedical research, and therefore, thorough characterization of murine drug metabolism is desired. The purpose of the present study was to determine both tissue- and gender-specific UGT gene expression profiles in mice. RNA from 14 tissues was isolated from male and female C57BL/6 mice and UGT expression was determined by the branched DNA signal amplification assay. UGTs highly expressed in mouse liver include Ugt1a1, Ugt1a5, Ugt1a6, Ugt1a9, Ugt2a3, Ugt2b1, Ugt2b5/37/38, Ugt2b34, Ugt2b35, and Ugt2b36. Several isoforms were expressed in the gastrointestinal (GI) tract, including Ugt1a6, Ugt1a7c, Ugt2a3, Ugt2b34, and Ugt2b35. In kidney, Ugt1a2, Ugt1a7c, Ugt2b5/37/38, Ugt2b35, and Ugt3a1/2 were expressed. UGT expression was also observed in other tissues: lung (Ugt1a6), brain (Ugt2b35), testis and ovary (Ugt1a6 and Ugt2b35), and nasal epithelia (Ugt2a1/2). Male-predominant expression was observed for Ugt2b1 in liver, Ugt2b5/37/38 in kidney, and Ugt1a6 in lung. Female-predominant expression was observed for Ugt1a1 and Ugt1a5 in liver, Ugt1a2 in kidney, Ugt2b35 in brain, and Ugt2a1/2 in nasal epithelia. UDP-glucose pyrophosphorylase was highly expressed in liver, kidney, and GI tract, whereas UDP-glucose dehydrogenase was highly expressed in the GI tract. In conclusion, marked differences in tissue- and gender-specific expression patterns of UGTs exist in mice, potentially influencing drug metabolism and pharmacokinetics.