The development of biological effects based tests in eels and mice and their application

Risk assessment methodologies that can distinguish between adverse and acceptable chemical induced biological effects will provide powerful tools for environmental agencies to use in conjunction with standardised technologies to manage chemical contamination effectively. To advance this technology in New Zealand, the following research describes a step-wise approach to develop and establish a suite of biological effect tests in the indigenous shortfinned eel (Anguilla australis) and the laboratory mouse (C57BL/6 strain). Mice were exposed to polyaromatic hydrocarbons (PAHs) directly (via intraperitoneal [ip.] injection to benzo[a]pyrene [B[a]P or benz(a)anthracene [BA]), or indirectly (via clean soil spiked with B[a]P or BA and to soil from contaminated sites). Mice treated with multiple ip. doses of B[a]P (100mg/kg) had significantly increased liver microsomal ethoxyresorufin O-deethylase (EROD) activity and cytochrome P450 concentration (P450 content), and hepatic-somatic index (HSI) compared to control. In contrast, EROD activity following ip. exposure to BA (100mg/kg) was 1 0-15-fold less than for B[a]P, suggesting a higher affinity of B[a]P to the Ah receptor. When mice were exposed to soil artificially contaminated with two environmentally relevant doses of B[a]P and BA biomarker responses were not significantly different from controls. The inherent ability of soil to reduce chemical bioavailability, is probably the major contributing factor for this result. However, mice exposed to contaminated soil from a fuel loading site (MP 0) and soil, from the gasworks site (PW) resulted in a significant increase in EROD activity of 2-fold and 4-fold respectively, compared to the controls. The total petroleum hydrocarbon (TPH) concentration of MP 0 soil was two times higher than the PW soil, which also directly correlates to the difference in EROD activity between mice exposed to these two soils. Although PW soil had a total PAH loading that was two orders of magnitude greater than MP 0 soil, the body burdens in mice exposed to these two soils were similar. Eels were exposed to one of a range of compounds (B[a]P, Aroclor 1254, 17β-estradiol [E2], 4- nonylphenol [4-NP], or chlorpyrifos [CP]) via ip. injection, or caged at sites that were potentially contaminated. Liver microsomal EROD activity of eels treated with multiple doses of B[a]P (1 and 10mg/kg) and Aroclor 1254 (10 and 100mg/kg) was significantly increased compared to the controls. Total P450 levels followed similar trends to EROD activity, but were not statistically significant. The induction of eel plasma vitellogenin (Vtg) following multiple ip. doses of E2 (100mg/kg) was marked in ip. experiment 1. However, a reduction in Vtg induction following an identical E2 exposure in ip. experiment 2 suggests that other cues such as seasonal changes, and or, sexually immature dimorphism may be involved. A small increase in plasma Vtg concentration was measured following exposure to 4-NP but this was not significant. Plasma acetylcholinesterase (AChE) activity of eel was slightly inhibited following ip. exposure to CP, but brain AChE was not affected by this or any other test compound. Similarly liver glutathione S-transferase (GST) did not respond to any treatments. Eels caged at a potentially impacted site on the Heathcote River showed significantly greater levels of EROD activity compared to an upstream site on the Heathcote River. While trends in the other biomarker responses were apparent in the eels caged at the potentially impacted Heathcote site, none were significant. Similarly, no significant differences between other potentially impacted and pristine sites were observed for any of the other biomarkers tested. The sensitivity of EROD activity to a range of compounds when exposed in the laboratory and field was demonstrated in both animal models. While mixed responses were observed for the other biomarkers, it is clear that further research is required to determine their suitability as a monitoring tool in these two test species.