Relationship Among DNA Adducts, Micronuclei, and Fitness Parameters in Xenopus laevis Exposed to Benzo[a]pyrene

The relationships between DNA adducts, micronuclei, and fitness parameters were examined in the amphibian, Xenopus laevis, exposed continuously to benzo[a]pyrene (B[a]P). While no DNA adducts were detected in the liver of control larvae, treatment for 12 d with varying concentrations of B[a]P produced three DNA adducts in liver cells. The level of these adducts was dependent on the treatment concentration. Frequencies of micronuclei were strongly affected in both the timed-exposure and metamorphosis experiments. Exposure to 248 nM B[a]P significantly affected the number of days required to attain metamorphosis. Wet weight differed among B[a]P doses after 14 d, but not at metamorphosis. Trends in levels of DNA adducts and micronuclei showed general inverse relationships to wet weight and developmental stage in the timed-exposure experiment. They also appeared to be associated negatively with wet weight at 14 d in the metamorphosis experiment, but not at metamorphosis.