Induction of cytochrome P4501A in African brown house snake (Lamprophis fuliginosus) primary hepatocytes.

Although there have been numerous studies involving fish, birds, and mammals, little is known about the response of the cytochrome P4501A system of snakes to halogenated aromatic hydrocarbons (HAHs). The present study describes the induction of ethoxyresorufin-O-deethylase (EROD) in primary hepatocytes of the African brown house snake (Lamprophis fuliginosus). Hepatocytes were exposed in multiwell plates to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and four different non-ortho-substituted coplanar polychlorinated biphenyls (PCBs 77, 81, 126, and 169). Exposure to TCDD and PCB 126 resulted in a dose-dependent increase in EROD activity, with maximum inducible EROD activities of 177 +/- 56 (mean +/- SEM) and 101.1 +/- 55 pmol/min/mg protein for TCDD and PCB 126, respectively. None of the other PCBs caused a measurable induction of EROD, which suggests reduced inducibility of snake hepatocytes compared to some vertebrate taxa. Median effective concentrations (EC50s) were 0.16 +/- 0.03 nM for TCDD and 8.25 +/- 4.14 nM for PCB 126. The relative potency (REP20-80) range for PCB 126 was 0.044 to 0.046. Compared to results from in vitro systems using other vertebrate species, both the maximum inducibility and the REPs estimated for L. fuliginosus were within the same range as those reported for mammals and the more sensitive bird species but were greater than the values reported for most fish species. In conclusion, induction of EROD activity in primary hepatocytes appears to be a useful approach for evaluating the dioxin-like potencies of aryl hydrocarbon-receptor agonists in snakes. The test system offers a method for rapid screening of reptilian responsiveness to these compounds using smaller numbers of organisms than with in vivo studies, an important consideration for many declining reptile species.