Dietary Modulation of Plasma Bilirubin and of Hepatic Microsomal Lipid Peroxidation in the Gunn Rat

Abstract

An in vitro assay for the simultaneous measurement of lipid peroxidation (LPO) and bilirubin degradation (BRD) activities in rat liver microsomes has been developed; a good correlation between the 2 activities was observed (r = 0.78). In the Gunn rat a lipid free diet caused an increase in plasma bilirubin (62.4 +/- 25.8%, n = 6) and a concomitant decrease in both hepatic microsomal LPO and BRD to zero. In contrast, on a 25% lipid diet there was a decrease in plasma bilirubin (46.1 +/- 3.6%; n = 8) associated with an increase in LPO (1.26 +/- 0.11 nmol/min/mg protein, and BRD (0.21 +/- 0.6 nmol/min/mg protein). Therefore, in the absence of bilirubin glucuronidation, dietary modulation of plasma bilirubin and lipid peroxidation appear to be closely associated.