Bilirubin accumulation and Cyp mRNA expression in selected brain regions of jaundiced Gunn rat pups.

INTRODUCTION

Few data exist on regional brain bilirubin content in the neonatal period when acute bilirubin-induced neurologic damage (BIND) may occur, and no information is available on regional brain expression of cytochrome P450 monooxygenases (Cyps) that oxidize bilirubin.

METHODS

Bilirubin content was analyzed by high-performance liquid chromatography and Cyp1a1, 1a2, and 2a3 mRNA expression was analyzed by quantitative PCR (qPCR) in cortex (Cx), cerebellum (Cll), superior colliculi (SC), and inferior colliculi (IC) of 17-d-old hyperbilirubinemic (jj) Gunn rat pups before and after administration of sulphadimethoxine to acutely displace bilirubin from plasma albumin.

RESULTS

There was no difference in bilirubin content among brain regions in untreated rats. After intraperitoneal sulphadimethoxine, bilirubin content peaked at fourfold in Cx and SC at 1 h; but at 11- to 13-fold in Cll and IC at 24 h; returning to control levels at 72 h. The Cyp mRNA peaked at 30-70 times control at 1 h in Cx and SC, but at 3-9 times control at 24 h in Cll and IC.

DISCUSSION: The close relationship in distinct brain regions between the extent of bilirubin accumulation and induction of mRNA of Cyps suggests Cyps may have a role in protecting selected brain areas from bilirubin neurotoxicity.