Exposure of Northern Leopard Frogs in the Green Bay Ecosystem to Polychlorinated Biphenyls, Polychlorinated Dibenzo-P-Dioxins, and Polychlorinated Dibenzofurans Is Measured by Direct Chemistry but Not Hepatic Ethoxyresorufin-O-Deethylase Activity

Abstract

We measured concentrations of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) in northern leopard frogs collected from the Green Bay ecosystem and explored the catalytic activity of hepatic cytochrome P450-associated monooxygenase (P450 enzyme) as a biomarker for exposure to aryl hydrocarbon receptor (AhR) agonists. The two hypotheses tested were PCH concentrations in northern leopard frogs would be positively correlated with sediment polychlorinated hydrocarbon (PCH) levels in wetland habitats along a contamination gradient and hepatic ethoxyresorufin-O-deethylase (EROD) activity of northern leopard frogs, which is presumably mediated by aryl hydrocarbon receptor (AhR), would be positively correlated with PCH concentrations in frog carcasses (whole body minus liver) from different collection sites. In 1994 to 1995, frogs from seven sites along the lower Fox River and Green Bay, USA, were assayed for hepatic EROD activities and whole carcass concentrations of PCBs, PCDDs, and PCDFs. Tissue total PCB concentrations ranging from 3 to 154 ng/g were significantly correlated with sediment PCB levels. Only one PCDD and two PCDFs at concentrations of 6 to 8 pg/g were found in the frogs collected from one of the sites. The EROD activity in frogs ranging from 186 to 270 pmol/min/mg protein was not significantly correlated with frog body weight and was similar among sites except for Peter's Marsh. No significant correlation was found between EROD activity and carcass PCB concentration. This result was consistent with the fact that the frogs collected from the Green Bay ecosystem had relatively low PCB concentrations compared with what was required for induction in the laboratory (ED50 for EROD is between 700 and 2,300 ng/g).

Congener‐specific analysis of polychlorinated dibenzo‐p‐dioxins, dibenzofurans, and coplanar polychlorinated biphenyls in frogs and their habitats, Kitakyushu, Japan

“…2), it was clear that PCDD/PCDF concentrations in frogs clearly reflected the concentration levels in their habitats. These findings confirm those reported by Huang et al [15].…”

Field exposure of frog embryos and tadpoles along a pollution gradient in the Fox River and Green Bay ecosystem in Wisconsin, USA

“…For this and past studies [7], we used sediment PCB and heavy‐metal concentrations, which are associated [1], as an index to the relative level of contamination at the sites. In 1994 and 1995, we collected sediment samples (depth, top 5 cm) from around the edge of the enclosures that we installed at the field sites, although sediment PCB data were from other sources for sites C1 and C3 [2] and site R1 (K.A.…”

“…Body burdens of PCBs, their possible relation to sediment contamination, and the sensitivity of amphibians to these compounds in the field are relatively unknown and are not easily predicted or approximated [6]. Two studies [7,8] found that levels of PCBs in adult leopard frogs ( Rana pipiens ) and green frogs ( Rana clamitans melanota ) were positively correlated with levels in sediments ( n = 5 sites each). We have extended these studies by performing PCB congener‐specific analyses on tadpoles and metamorphosed frogs raised at many sites and on the embryo batches from which they were derived.…”

Do hormone‐modulating chemicals impact on reproduction and development of wild amphibians?

“…Despite a reported association between intersex and polychlorinated dibenzofurans in A. crepitans in Illinois over 15 years ago (Reeder et al ., ) and the associations between industrial contaminants and intersex detailed above (Reeder et al ., ; Skelly et al ., ), evidence for endocrine disruption in wild anurans for non‐pesticidal pollutants is scarce. Contaminants, including BPA, PCBs and phthalates are present in anuran environments (Oehlmann, Oetken & Schulte‐Oehlmann, ), and some have been detected in anuran tissue (Huang et al ., ; Karasov et al ., ). Furthermore, there are indications that PCB levels found in anuran tissue may affect reproductive endpoints (Jofre & Karasov, ).…”