Nonbacterial transformation of bilirubin in bile

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Abstract
Bilirubin present in gallstones is mainly in the unconjugated form despite the frequent absence of bacteria in bile. The aim of the present study was to determine if nonbacterial β-glucuronidase activity and/or nonenzymatic hydrolysis is responsible. Inflammatory cells such as polymorphonuclear leukocytes and lymphocytes appearing with the presence of brown pigment gallstones and inflammation in biliary tract was shown to effect deconjugation of bilirubin conjugates in bile and contribute to their formation in addition to that of bacterial β-glucuronidase. Gallbladder bile (mean±sd, 4.0±1.6%, N=29)contained more unconjugated bilirubin than hepatic bile (mean±sd, 2.7±1.1%).In vitro experiments showed the deconjugation to take place during incubation at 37°C without the presence of bacteria. Therefore, transformation of conjugated to unconjugated bilirubin is likely to take placein vivo during the storage in gallbladder, and nonbacterial β-glucuronidase activity and/or nonenzymatic hydrolysis may be responsible for such transformation.