138 BILIRUBIN PHOTOISOMERIZATION PRODUCTS IN URINE FROM A CRICLER-NAJAR TYPE 1 PATIENT

Crigler-Najjar type I syndrome (C.-N.s.) is a rare anomaly of bilirubin (BR) metabolism characterized by life-long hyperbilirubinemia. Phototherapy (PT) is the only treatment of value in the long-term management of C.-N.s.. In this study, we have analyzed the BR photoisomer composition in urine of a 18 year-old girl with C.-N.s., before, during and after PT administered with Philips F40T12/BB ‘special’ blue fluorescent lamps. The HPLC analysis of serum samples indicates that only native BR and its configurational isomer, 4Z,15E-BR, were present, with a relative steady-state concentration of about 24% of 4Z,15E-BR during PT. In urine, both configurational and structural [lumirubin, (15Z-LR + 15E-LK)] isomers were found before and, with increasing concentrations, during PT. Before PT, the total amount of structural isomer pool (15Z-LR+15E-LR) was as much as 3 times higher than configurational pool (4Z,15E-BR+4E, 15Z+BR+4Z,15Z-BR). This proportion did not change when the patient was exposed to PT light, although the total pigment concentration in urine increased markedly. This study suggests that the BR photo-product elimination in this adult with C.N.s. is significantly different than in the neonates. In fact, 15Z-LR (1-4%) and traces of 4E-15Z-BR are detected in serum of icteric babies exposed to PT, along with 4Z,15Z-BR and 4Z,15E-BR. On the other hand, the urine of icteric infants contains very small concentrations of the configurational pool. These evidences show that in C.-N.s. mechanisms exist to excrete all BR photoisomers. The existence of a relevant fraction of configurational photoisomers in urine suggests that their contribution to the mechanism of action of PT in C.-N.s. is not negligible.