Bucolome N-glucuronide (BCP-NG, main metabolite of bucolome (BCP) is the first N-glucuronide of barbituric acid derivatives isolated from rat bile. The objective of this study was to identify the main tissue producing BCP-NG and the molecular species of BCP-NG-producing UGT. Four target tissues were investigated: the liver, small and large intestines, and kidney. To identify the UGT molecular species responsible for BCP-NG formation, yeast microsomes expressing each rat UGT isoform were prepared. BCP-NG formation was detected in all microsomal fractions of the 4 tissues. The liver microsomal BCP-NG-producing activity was the highest, followed by that in the small intestinal microsomes, showing about 41% of the liver microsomal activity level. BCP-NG-producing activity (min-1) was determined in yeast microsomal fractions expressing rat UGT isoforms, and the activity was detected in UGT1A1

The barbituric acid derivative bucolome (BCP) is a nonsteroidal anti-inflammatory drug. The present study investigated (hUGT1A1, 1A3, 1A4, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7, 2B15, and 2B17). As a result, BCP-NG formation (pmol equivalents/min/mg protein) was observed with microsomes expressing hUGT1A1 (142), 1A3 (196), 1A4 (8), 1A7 (8), 1A8 (66), 1A9 (38), 1A10 (9), 2B4 (7) and 2B7 (16). In particular, the activity of hUGT1A1 and 1A3 was high. These results suggest that the UGT isoforms responsible for formation of BCP-NG exist in various mammalian species, including humans, and that the UGT 1A family is primarily responsible for BCP N-glucuronide formation in humans. In order to identify the UGT isoforms involved in formation of BCP-NG in humans, we investigated BCP-NG formation by the microsomes of insect cells expressing each of twelve UGT isoforms