Gunn rats: a reproducible experimental model to compare the different methods of measurements of bilirubin serum concentration and to evaluate the risk of bilirubin encephalopathy

Three groups of Gunn rats were studied: group 1 was perfused with bilirubin solution alone, group 2 was perfused with bilirubin and albumin solutions simultaneously, group 3 was perfused with bilirubin solution for 30 min then bilirubin and albumin solutions for the following 10 min. Our results indicate that (1) Gunn rats are a reliable experimental model to study the risk of bilirubin encephalopathy, (2) unbound bilirubin can enter the brain when albumin binding capacity is reduced, (3) and bilirubin binding capacity of serum for unbound unconjugated serum bilirubin is a better criterion than total serum bilirubin and erythrocyte bilirubin to evaluate the risk of kernicterus. This model could also be used to study variations of permeability of the blood-brain-barrier and influences of drugs on bilirubin metabolism.