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USE OF WHOLE BODY CHEMICAL RESIDUE ANALYSIS AND LASER SCREENING CONFOCAL MICROSCOPY TO DESCRIBE DISTRIBUTION OF PBTS IN FISH EARLY LIFE STAGES
Citation:
Hornung, M. W., P. M. Cook, AND J W. Nichols. USE OF WHOLE BODY CHEMICAL RESIDUE ANALYSIS AND LASER SCREENING CONFOCAL MICROSCOPY TO DESCRIBE DISTRIBUTION OF PBTS IN FISH EARLY LIFE STAGES. Presented at Society of Toxicology 42nd Annual Meeting, Salt Lake City, UT, March 9-13, 2003.
Description:
Fish early life stages (ELS) are more sensitive than juveniles or adults to many persistent bioaccumulative toxicants (PBTs). To better understand the mechanisms by which these chemicals produce toxicity during fish ELS, dose-response relationships need to be determined in relation to the distribution of chemicals in sensitive tissues. In this study, whole-organism residue analysis was combined with in situ imaging using a multi-photon laser scanning confocal microscope (LSCM) to describe the tissue distribution of PBTs during fish ELS. The method was tested in Japanese medaka (Oryzias latipes) using pentamethyl-difluoro-boro-indacene (BODIPY), a model chemical having high fluorescence efficiency and a log Kow value near 5.0, and the polyaromatic hydrocarbon benzo[a]pyrene (BaP). Newly fertilized medaka eggs were exposed to BODIPY or BaP for 6 h immediately after fertilization followed by transfer to clean media for the duration of the experiment. The tissue distribution of fluorescent signal was compared to the whole-embryo chemical concentration at each time point. The fluorescent signal of BODIPY was initially very strong in yolk lipid droplets with moderate signal in the yolk. During development the fluorescent signal became diffusely distributed throughout the embryo with strong signal remaining in the yolk and yolk lipid droplets. As embryonic development progressed, fluorescence became evident in the gall bladder, bile ducts, and gut. The distribution of benzo[a]pyrene signal was similar to that of BODIPY at 1 d post-fertilization (dpf); however, by 5 dpf much of the signal was gone from the lipid droplets, and strong signal was observed in the bile ducts, gall bladder, and gut. Analysis of tissue extracts indicated that BaP was metabolized during early development. This metabolism is thought to account for the difference in distribution of the two chemicals as determined with the LSCM. The LSCM is a useful tool for describing the tissue distribution of PBTs during fish ELS and can be employed to understand how metabolism affects this distribution. This abstract does not necessarily reflect EPA policy.