In Vitro Kinetic Studies on Gamma Irradiation of Aqueous Bilirubin in the Presence and Absence of Oxygen

Abstract Bilirubin is associated with positive and negative biological effects. The health effect of bilirubin, in depleting elevated levels of peroxyl radicals in cells, has recently come to the fore. On the other hand, bilirubin is linked to jaundice and the mechanism of bilirubin phototherapy treatment involves isolation of the bilirubin from the subject by means of photoisomerization and conversion to biliverdin. In both cases, the reversion of biliverdin to the parent specimen and its conversion to other undesirable isomers is complex, and therefore, there is a biological need to study such biliverdin isomers exclusively, in the absence of photolytical and unwanted chemical effects. Gamma‐induced (137Cs source) depletion of bilirubin under oxic (in air and O2) and anoxic (N2) conditions was investigated, and led to the exclusive co‐production of the “short‐wavelength” isomer of biliverdin. The depletion of the unconjugated specimen (4.0 × 10−2 mM in 0.05 M aqueous NaOH) was monitored spectrophotometr...