A model for brain bilirubin uptake (BBU) predicts that BBU in jaundiced newborns typically depends on the plasma total bilirubin concentration (TBC) and the bilirubin- albumin dissociation rate constant (k1) rather th...A model for brain bilirubin uptake (BBU) predicts that BBU in jaundiced newborns typically depends on the plasma total bilirubin concentration (TBC) and the bilirubin- albumin dissociation rate constant (k1) rather than the unbound bilirubin (Bf). The model’ s validity was tested by 1) evaluating its requirement that k3 and k2, where k3 and k2 are the rate constants for BBU and B f- albumin association, respectively, and 2) determining whether the calculated BBU is ≤ 5% of the bilirubin production rate, the approximate BBU expected if brain bilirubin levels are < 1% of the miscible bilirubin pool as reported in the literature. The model was investigated using peroxidase test measurements of TBC, Bf, k1, and k2 from 185 jaundiced newborns. Mean k2 was compared with the reported k 3 value of 0.08/s. BBU calculated from TBC and k1 was expected to be ≤ 0.005 μ g/kg/s given the reported bilirubin production rate of 0.1 μ g/kg/s. BBU calculated using Bf was also compared with the bilirubin production rate. The mean k2 of 8.9 L/μ mol/s was greater than k3, and the mean BBU of 0.72 μ g/kg/s exceeded the expected range of ≤ 0.005 μ g/kg/s. However, mean BBU using Bf (0.00073 μ g/kg/s) was within the expected range. A mathematical model calculating BBU as a function of TBC and k1 could not be validated. BBU calculated from Bf is consistent with the observation that < 1% of the miscible bilirubin pool is distributed in the brain.展开更多
文摘A model for brain bilirubin uptake (BBU) predicts that BBU in jaundiced newborns typically depends on the plasma total bilirubin concentration (TBC) and the bilirubin- albumin dissociation rate constant (k1) rather than the unbound bilirubin (Bf). The model’ s validity was tested by 1) evaluating its requirement that k3 and k2, where k3 and k2 are the rate constants for BBU and B f- albumin association, respectively, and 2) determining whether the calculated BBU is ≤ 5% of the bilirubin production rate, the approximate BBU expected if brain bilirubin levels are < 1% of the miscible bilirubin pool as reported in the literature. The model was investigated using peroxidase test measurements of TBC, Bf, k1, and k2 from 185 jaundiced newborns. Mean k2 was compared with the reported k 3 value of 0.08/s. BBU calculated from TBC and k1 was expected to be ≤ 0.005 μ g/kg/s given the reported bilirubin production rate of 0.1 μ g/kg/s. BBU calculated using Bf was also compared with the bilirubin production rate. The mean k2 of 8.9 L/μ mol/s was greater than k3, and the mean BBU of 0.72 μ g/kg/s exceeded the expected range of ≤ 0.005 μ g/kg/s. However, mean BBU using Bf (0.00073 μ g/kg/s) was within the expected range. A mathematical model calculating BBU as a function of TBC and k1 could not be validated. BBU calculated from Bf is consistent with the observation that < 1% of the miscible bilirubin pool is distributed in the brain.
