Effects of thermostability of bilirubin subfractions on serum bilirubin measurement

Bilirubin is sensitive to light and oxygen. The rate of photodegradation of unconjugated bilirubin (Bu) was nearly twice that of monoconjugated bilirubin (mBc) and three fold that of diconjugated bilirubin (dBc); delta bilirubin (Bd) was the most stable against photoirradiation. In the presence of serum albumin, conjugated bilirubin (Bc: i.e., mBc and dBc) showed the highest rate of oxidation by peroxidase oxidation and bilirubin oxidase oxidation followed by Bu and Bd. The thermolability of bilirubin was reported by Morishita et al.. They reported that the values of Bc and TB decreased gradually as the temperature and/or time increased, and the values of Bu increased over a 2-day period at four temperatures: -20, 4, 25 and 37°C. However, little information is available regarding the stability of bilirubin subfractions within a short time period. The aim of this study is to investigate how bilirubin subfractions are destroyed by heat during 1.5, 3 and 6 hours of storage in the dark at 4°C (refrigerator), 25°C (room temperJournal of Analytical Bio-Science Vol. 33, No 3 (2010)