PM10 Mechanisms of Toxic Action
Exhibit Hall
8:00 AM - Monday
(PM157) Biliverdin in bile samples: biomarker for oxidative stress and use in bile fluorescence analysis.
van den Hurk, P1, 1 Clemson University, Environmental Toxicology, Pendleton, SC, USA
ABSTRACT- In recent years, the measurement of bile fluorescence has become a popular biomarker to demonstrate the exposure of fish to polynuclear aromatic hydrocarbons. The method is relatively simple to perform, and has been validated in dosing studies. However, because bile volume is highly variable and dependent on feeding intervals, normalization of the fluorescence units has been a problem. Bile protein amounts and biliverdin absorption have been used for normalization, but appear to be unreliable. The objective of this study was to investigate the relationship between protein levels and biliverdin concentrations in bile samples from fish under different chemical stressors. In two separate experiments channel catfish were dosed with mixtures of benzo[a]pyrene (BaP) and cadmium, chlorinated phenols and borneol. The results show a linear relationship between bile protein and biliverdin for each treatment group. The amount of biliverdin appears to be directly related to the amount of protein in the bile. However, the slope of this relationship was significantly increased when fish received more chemical stress. The slope for the BaP alone treatment was higher than the one for the control group. And the combined BaP with other toxicants was significantly higher than the BaP alone treatment. Thus, under increasing toxicant stress, more biliverdin is excreted per amount of protein. This process can be explained by the knowledge that biliverdin is the precursor for bilirubin, an insoluble breakdown product of hemoglobin, and a powerful antioxidant. Heme containing proteins are metabolized by heme oxygenase (HO). Several chemical stressors are known to upregulate HO activity, thus increasing the production of biliverdin and bilirubin. Future experiments will further investigate the relationship between HO induction and biliverdin concentrations in bile. Meanwhile, based on the results presented here, bile fluorescence is better expressed per amount of bile protein than per bilirubin absorption.
Key words: biliverdin, bile , fluorescence, heme oxygenase