Bilirubin toxicity produces changes in BAEPs which are more likely to correlate with serum non-albumin bound bilirubin (NAB) than total bilirubin(TB) levels. We therefore hypothesized that BAEP changes in jaundiced Gunn rat pups would correlate better with NAB or NAB/TB ratio than with TB. BAEPs, TB, NAB, and NAB/TB ratios were measured in 13 Gunn rat pups weighing 26.8±2.0g at 16±0.5 days of age. BAEPs were obtained with 75 dBHL monaural clicks to the right and left ears under ketamine and acepromazine anesthesia. The I-II interwave interval (BAEP wave II - wave I latency) is the average from right and left ears; its increase is a sensitive indicator of bilirubin toxicity. Initial serum TB was measured by the diazo test and NAB by combining the diazo and peroxidase tests. For the peroxidase test, peroxide and peroxidase were added to 25 μl of serum to give dilutions of 1:2.4. After 1 min of oxidation, diazo reagent was added to stop the reaction and the final TB measured. The initial TB, final TB, and peroxidase rate constant were used to calculate NAB. Correlations of TB, NAB, and NAB/TB with I-II were then tested. Increases in I-II correlated positively with the NAB/TB ratio (F9.4, r2=0.48, p<0.01). NAB correlated positively with increasing I-II (r2=0.42,p=0.016). Gunn rat pups are a useful model for studying the role of bilirubinalbumin binding in bilirubin toxicity as detected by BAEP.

{\i Supported by NIH R01 DC33069.} Figure

figure 1