A Comparative Study of Three Alternative Avian Toxicity Testing Methods: Effects on Hepatic Gene Expression in the Chicken Embryo.

Abstract

There is growing interest in developing alternative methods to screen and prioritize chemical hazards though few studies have compared responses across different methods. The objective of this study was to compare three alternative liver methods derived from White Leghorn Chicken (Gallus gallus domesticus): primary hepatocyte culture, liver slices, and liver from in ovo injected embryos. We examined hepatic gene expression changes upon exposure to three chemicals (17β-Trenbolone (17βT), 17β-Estradiol (E2), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)) using a custom qPCR array with seven genes (VTG, Apo, CYP1A4, LBFABP, HSD3β1, SCD, SULT1E1). Gene expression across the three methods were examined using hierarchical clustering. CYP1A4 up-regulation in response to TCDD was consistent across all methods, and the magnitude was higher in hepatocytes (>150-fold) compared to slices (>31-fold) and in ovo liver (>27-fold). In hepatocytes, SCD and VTG up-regulation in response to 17βT and E2 were >4-fold and 16-fold, respectively. The rank order of cases with significant changes in gene expression among the three methods was: hepatocytes (22) > in ovo liver (11) > liver slices (6). Hierarchical clustering grouped liver slices and in ovo liver as more similar, while hepatocytes were grouped separately from in ovo liver. More introspective comparisons are needed to understand how and why alternative methods differ and aid in their integration into toxicity testing. This article is protected by copyright. All rights reserved.