Uptake, depuration, and biotransformation of anthracene and benzo[a]pyrene in bluegill sunfish

Bluegills (Lepomis macrochirus Raf.) were exposed to [14C]anthracene or [14C]benzo[a]pyrene (B[a]P) in water. Rates of uptake and biotransformation within the fish were followed by 14C counting and thin-layer and liquid chromatography. The initial uptake-rate coefficient for anthracene (KU = 36 hr-1) was found to be independent of exposure concentration. The presence of dissolved humics did not affect anthracene uptake but did reduce the B[a]P uptake rate significantly. Biotransformation of the anthracene was constant at 0.22 nmol/g/hr, with approximately 92% of the residue unmetabolized at 4 hr. Uptake of B[a]P was linear (KU = 49 hr-1), although biotransformation increased from 0.044 to 0.088 nmol/g/hr between 1 and 2 hr of exposure. Only 11% of the B[a]P 14C activity at 4 hr represented the parent compound. Although 6% of the anthracene was found in liver and gall bladder, 25% of the B[a]P was distributed in the two organs. Depuration rates were first order and yielded half-lives of 17 hr for anthracene and 67 hr for B[a]P. The estimated bioconcentration factors (BCF) for anthracene and B[a]P in whole fish (KU/KD) were 900 and 4900, respectively, for total 14C activity, but only 675 and 490 for parent material. These BCFs were considerably lower than those predicted from the octanol-water partition coefficients because of biotransformation.