Branchial elimination of superhydrophobic organic compounds by rainbow trout (Oncorhynchus mykiss)

The branchial elimination of pentachloroethane and four congeneric polychlorinated biphenyls by rainbow trout was measured using a fish respirometer-metabolism chamber and an adsorption resin column. Branchial elimination was characterized by calculating a set of apparent in vivo blood:water partition coefficients (P-BW). Linear regression was performed on the logarithms of P-BW estimates and the log K-OW value for each compound to give the fitted equation: 109 P-BW = 0.76-log K-OW - 1.0 (r(2) = 0.98). The linear nature of this relationship provides support for existing models of chemical flux at fish gills and suggests that a near equilibrium condition was established between chemical in venous blood entering the gills, including dissolved and bound forms, and dissolved chemical in expired branchial water. In Vivo P-BW estimates were combined with P-BW values determined in vitro for a set of lower log Kw compounds (Bertelson et al., Environ. Toxicol. Chem. 17 (1998) 1447-1455) to give the fitted relationship: log P-BW = 0.73-log K-OW - 0.88 (r(2) = 0.98), The slope of this equation is consistent with the suggestion that chemical binding to non-lipid organic material contributes substantially to blood:water chemical partitioning. An equation based on the composition of trout blood (water content and the total amount of organic material) was then derived to predict blood:water partitioning for compounds with log K-OW values ranging from 0 to 8: log P-BW = log [(10(0.73 log KOW.)0.16) + 0.84], Published by Elsevier Science BN.