[Photoisomers of bilirubin in the blood of neonates during phototherapy].

In a group of mature neonates with hyperbilirubinaemia the authors investigated by chromatography, using the HPLC method, levels of bilirubin photoisomers before phototherapy, in the course of phototherapy and after its termination. The configuration isomer 4 Z, 15 E is detected in blood of all icteric neonates already before the onset of treatment in a mean concentration of 5.2 (s = 3.8) mumol/l, during phototherapy its mean concentration is 23.0 (s = 8.0) mumol/l. Photoisomers participate in non-conjugated bilirubinaemia on average by 10%: 92% are formed by isomer 4 Z, 15 E, 5% by isomer 4 E, 15 Z and 3% by the structural isomer lumirubin. On the day following discontinuation of treatment the mean photoisomer concentrations are significantly lower than during phototherapy and significantly higher than before its initiation.