ARTICLE pubs.acs.org/est
Tissue Distribution and Depuration Kinetics of Waterborne 14 C-labeled Light PAHs in Mummichog (Fundulus heteroclitus) . Pelletier,‡ and C. Rouleau§,* F. X. Valdez Domingos,†,‡ C.A. Oliveira Ribeiro,† E †
Departamento de Biologia Celular, Universidade Federal do Parana, C.P. 19031, CEP: 81531-970 Curitiba PR, Brazil Institut des Sciences de la Mer de Rimouski, Universite du Quebec a Rimouski, 310 allee des Ursulines Rimouski (Quebec), Canada G5L 3A1 § Maurice-Lamontagne Institute Fisheries and Oceans Canada, 850 route de la mer Mont-Joli (Quebec), Canada G5H 3Z4 ‡
bS Supporting Information ABSTRACT: Light polycyclic aromatic hydrocarbons (PAHs) of petrogenic origin are commonly found in estuaries and coastal areas. Though they are known to be toxic to fish, little is known about their uptake and tissue distribution. This paper reports on the results of a study on uptake, elimination, and tissue distribution of three waterborne 14C-labeled PAHs in the mummichog, Fundulus heteroclitus, using whole-body autoradiography. After a 24 h exposure to 1 μCi 3 L1 of 14Cnaphthalene, 14C-1-naphthol, and 14C-phenanthrene, fish were transferred to clean water and tissue distribution examined after 0, 1, 3, 7, 14, and 21 days of depuration. All compounds were readily accumulated by fish and were also rapidly eliminated (t0.5 range = 1.1 to 3.0 days). Most of the radioactivity in naphthalene- and phenanthrene-treated fish was found in gall bladder . liver > intestinal lumen. In naphthol-exposed fish, an important labeling of some brain areas was observed. Brain of naphthalene-exposed fish was also labeled after 24 h depuration, indicating that exposure to naphthalene may result in metabolite accumulation in the brain. This is the first study showing that naphthalene, naphthol, and/or unidentified metabolite(s) can accumulate in brain tissues, which may impair normal brain function.
’ INTRODUCTION Petroleum residues from urban and industrial effluents, marine traffic, and oil spills represent the main sources of polycyclic aromatic hydrocarbons (PAHs) in estuaries and marine coastal areas. This can be a serious concern for human health as edible fish can absorb PAHs.13 Because of their high water solubility, high volatility, and biodegradability, small PAHs (2 and 3 rings) remain in environmental compartments for a shorter period compared to larger ones but they still represent a toxic potential for aquatic organisms.2,4 Although light PAHs are often considered as being easily degraded by organisms1 they can be found along with their metabolites in contaminated water and sediment,5,6 as well as fish.712 The watersoluble fraction (WSF) of crude oil, which contains light PAHs, is known to affect survival, growth, reproduction, and metabolism in marine organisms 1316 and to induce histopathologic lesions.2 Nevertheless, little is known about the detailed tissue distribution of light PAHs in fish. Detection and precise location of PAHs in small tissues and organs represent a difficult and time-consuming task when using post mortem dissection and chemical analysis. Analytical methods for PAHs and their metabolites are labor intensive techniques requiring at least 100 mg samples.17 An alternative approach is to use 3H- and 14C-radiolabeled PAHs.1824 Their quantification by liquid scintillation counting is quite simple and it can be combined with thin-layer chromatography to obtain data about r 2011 American Chemical Society
PAH metabolites.1,25 Nevertheless, experimental work is usually limited to a number of selected organs and drawbacks of classical dissection remain present, for example, cross-contamination and difficulty to sample small or diffuse organs and tissues. Whole-body autoradiography (WBARG) allows visualizing the distribution of a radiolabeled chemical in thin cryosections of a whole animal.26 Radiolabel distribution in tissues is preserved by collecting sections of a frozen specimen on adhesive tape, followed by freeze-drying without any chemical treatment. Tissue sections are then exposed on radiation sensitive imaging plates which yield a high-resolution (ca. 0.1 mm) image of the distribution of the compound under study. By cutting thin sections at different levels in the animal, almost all organs and tissues can be sampled and imaged. Though WBARG does not allow distinguishing parent compound from its metabolites, it provides very reliable quantitative tissue distribution data27 that may reveal unforeseen sites of accumulation. This technique has been successfully used in our laboratory to study the uptake and distribution of radiolabellled contaminants in a number of aquatic organisms.2832 Received: September 15, 2010 Accepted: February 25, 2011 Revised: February 23, 2011 Published: March 09, 2011 2684
dx.doi.org/10.1021/es103133h | Environ. Sci. Technol. 2011, 45, 2684–2690
Environmental Science & Technology
ARTICLE
Table 1. Elimination Kinetic Parameters ((S.E.) Calculated by Least Square-Linear Regression Analysis (eq 1) with Autoradiographic Data from Liver and Gall Bladdera A0 DLU 3 mm2 3 h1 (kBq 3 g1w.w.) naphthalene (L) naphthalene (GB) naphthol (L) naphthol (GB) phenanthrene (L) phenanthrene (GB)
k d1
t0.5 d
r2
p
346 ( 36 (1.7 ( 0.2)
0.228 ( 0.015
a
3.0 ( 0.2
0.92
