Temperature and congener structure affect the enantioselectivity of toxaphene elimination by fish.
Recent advances in enantioselective separation techniques have enabled scientists to investigate environmental fate processes of chiral pollutants. In this study, congener- and enantiomer-specific toxaphene residues were monitored in captive, naturally contaminated fish (Fundulus heteroclitus) to characterize the effect of temperature and compound structure on the enantioselectivity of the elimination process. A previous study performed under warm water conditions (Tmean = 25 degrees C) demonstrated relatively rapid (t(1/2) approximately = 7-14 d) and enantioselective elimination of the reductive dechlorination metabolites 2-exo,3-endo,6-exo,8,9,-10-hexachlorobornane (B6-923 or Hx-Sed) and 2-endo,3-exo,5-endo,6-exo,8,9,10-heptachlorobornane (B7-1001 or Hp-Sed). As expected, repetition of this experiment at cooler water temperatures (Tmean = 15 degrees C) resulted in a decrease in overall (i.e., both enantiomers) first-order elimination rate constants. Enantiomer fractions or ratios (EFs/ERs) during elimination, however, varied by congener, ranging from racemic for very rapidly eliminated Cl5 homologues to increasingly nonracemic for selected Cl6-Cl8 homologues (including 86-923, several unknown Cl7 compounds, B8-1414, and B8-1945). As a result, we propose a classification to describe the environmental persistence of chiral toxaphene pollutants based on congener-specific elimination kinetics and susceptibility to biotransformation as measured by EFs/ERs.
Maruya
Keith A
KA
Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, Georgia 31411, USA. keithm@sccwrp.org
Smalling
Kelly L
KL
Vetter
Walter
W
D000818:Animals; D001711:Biotransformation; D001892:Camphanes / Q000737:chemistry / Q000378:metabolism; D002713:Chlorine / Q000737:chemistry / Q000378:metabolism; D005399:Fishes / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D007306:Insecticides / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D013237:Stereoisomerism; D013696:Temperature; D014112:Toxaphene / Q000737:chemistry / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
D001892:Camphanes; D007306:Insecticides; D014874:Water Pollutants, Chemical; D002713:Chlorine; D014112:Toxaphene