KC Ngai, CY Yeung, J Karlberg

Bilirubin toxicity is mainly manifested as central nervous system abnormalities in the neonate. This suggests a difference in the susceptibility to bilirubin cytotoxic effects by different tissues or cell-lines.

To test the validity of this clinical observation, we adopted the MTT (3-[4.5-dimethylthiazol-2-yl]-2.5-diphenyl tetrazolium bromide) method to study the cytotoxic effect of bilirubin on various commercially available cell-lines on culture. We have developed a new modification to the available methods by removing the interference of precipitated bilirubin in the culture medium. We are able to obtain consistently reproducible results for tests.

We have found that cytotoxic effects are usually demonstrated when certain bilirubin albumin molar ratio is exceeded in the medium of a growing cell line in culture. Different cell-lines exhibit different degree of susceptibility to bilirubin toxicity; neuroblastoma and glioblastoma cells are most susceptible and fibroblast the least vulnerable among the cells we have tested. Addition of Na-salicylate to increase the unbound bilirubin in the bilirubin-albumin solution has resulted in significant increase of cytotoxicity. Our findings confirm the clinical observations that unbound bilirubin is responsible for cell damage and different cells suffer different degree of cytotoxicity from bilirubin.