Exposure to the polychlorinated biphenyl mixture Aroclor 1254 alters melanocyte and tail muscle morphology in developing Xenopus laevis tadpoles.

Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that have damaging effects on both ecosystem and human health. Numerous studies have shown that exposure to PCBs can alter growth and development of aquatic organisms, including frogs. In this report, developing Xenopus laevis tadpoles were exposed to the PCB mixture Aroclor 1254. Tadpoles were exposed from 5 through 9 d postfertilization to either 0, 1, 10, 50, or 100 ppm Aroclor 1254. Exposure to an acute, high concentration of Aroclor 1254 (10, 50, and 100 ppm) caused statistically significant reductions in survival and body size. In addition, tadpoles exposed to these higher concentrations showed histological abnormalities, including aberrant tail tip, myotomal, and melanocyte morphologies. Described adverse health effects associated with PCB exposure of developing frogs will serve as useful health endpoints in ongoing and future molecular-based studies that correlate health effects with changes in gene expression.

Aroclor 1254 alters morphology, survival, and gene expression in Xenopus laevis tadpoles.

PCBs are persistent environmental contaminants that cause a variety of adverse health effects in wildlife and humans. This article describes the use of signature gene expression patterns that link increased PCB exposure with progressive, adverse biological effects. Developing Xenopus laevis tadpoles of two age classes were exposed to the PCB mixture Aroclor 1254 for 2 days. Real-time PCR was used to quantitate mRNA expression for 11 physiologically relevant, potential bioindicator genes. Younger tadpoles (5 days postfertilization) were resistant to Aroclor 1254 and showed few changes in gross morphology, swimming behavior, survival, or gene expression. Older tadpoles (11 days postfertilization) were more susceptible to Aroclor 1254. Exposure to 25 and 50 ppm Aroclor 1254 caused alterations in gross morphology and swimming behavior and statistically significant decreases in survival. These tadpoles showed statistically significant decreases in gene expression for 9 out of the 11 genes measured. Tadpoles exposed to 10 ppm showed incipient health changes but had gene expression profiles similar to the tadpoles treated with higher doses of Aroclor 1254. Tadpoles exposed to 1 ppm did not exhibit any observable adverse health effects, yet statistically significant decreases in gene expression occurred in these tadpoles (4 out of 11 genes). After prolonged exposure, tadpoles exposed to 1 and 10 ppm Aroclor 1254 exhibited health effects similar to those exposed to higher concentrations. Therefore, changes in expression of specific genes may serve not only as molecular bioindicators of Aroclor 1254 exposure but also as predictors of impending adverse health effects.