Lobular distribution of human liver phenol and bilirubin uridine 5'-diphosphate glucuronosyltransferase messenger RNAs

Background & Aims: Heterogeneity in uridine 5'-diphosphate (UDP) glucuronosyltransferase expression across the human hepatic acinus may be important in the manifestation of certain zone-specific chemical hepatotoxicities. Previous immunohistochemical studies suggested that a phenol transferase induced by polycyclic aromatic hydrocarbons may be differentially expressed in centrilobular hepatocytes of rats. The aim of this study was to assess the distribution of the phenol and bilirubin transferases in human liver at the RNA level. Methods: In situ RNA hybridization was used with two human liver samples and specific probes for the phenol transferase RNA, HLUG P1, and the bilirubin transferase RNAs, HUG-Br1 and HUG-Br2. Results: The highest density signals were observed for the bilirubin transferase RNAs, both appearing to be evenly expressed in hepatocytes across the liver lobule. Slightly higher density of HUG-Brl message was observed in some centrilobular hepatocytes surrounding larger central vein structures. HLUG P1 RNA was expressed at low levels (approximate to fivefold greater than background signal) and was evenly distributed. Conclusions: The data suggest that a species difference exists in the distribution of the human and rat phenol transferase. No evidence was found for significant zonation in the pattern of expression of either the phenol or bilirubin transferase genes in human liver.