Impairment of mitochondrial 5-aminolevulinic acid synthase activity in Gunn rat liver

Gunn rats are characterized by hereditary hyperbilirubinemia and a decrease, when compared to Wistar rats, in hepatic heme pool size which could result from an alteration of mitochondrial functions. Unconjugated bilirubin present in Gunn rat liver did not modify either the ultrastructural morphology or oxidative metabolism of the mitochondria as compared to those in Wistar rat liver. However, 5-aminolevulinic acid synthase activity is reduced by nearly 40% in Gunn rat liver mitochondria, thus explaining the reduced size of the hepatic heme pool.