Oral Bioavailability and Toxicokinetics of 3,39,4,49,5- Pentachlorobiphenyl in Northern Leopard Frogs, Rana Pipiens

This study is the first report on oral bioavailability, whole-body elimination, and distribution of a specific polychlorinated biphenyl (PCB) congener on an amphibian species, northern leopard frogs. Each frog was orally dosed once with either 0.35 or 5.0 mg/kg PCB 126 (based on frog wet wt), including tracer 14C-PCB 126 (39,49,59-phenyl-ring-14C) by force feeding it a cricket injected with the PCB. We found no statistical difference (t 5 0.917, df 5 5, p 5 0.401) in the average 48-h oral bioavailabilities of 0.35and 5.0-mg/kg dosage groups, which were 84.6 6 5.8% (mean 6 SE, n 5 4) and 90.9 6 1.5% (n 5 3), respectively. Statistical analysis indicated that time was the only independent variable affecting the retention of whole-body 14C content. Kinetics were apparently first order because elimination rate was independent of dose. Assuming a single pool and one elimination rate, the t1/2 value for whole-body elimination of PCB-derived 14C was 763 d. Liver, fat bodies (corpora adiposa), carcass (head, bone, cartilage materials, and residues of other tissues), skin, and muscle were the major organs for PCB 126 retention in both dosage groups. The concentrations of 14C residue in fat bodies were relatively constant throughout the experiment. However, total residues in fat bodies declined throughout the experiment in both dosage groups in correlation with declining masses of fat bodies. Gonad, kidney, stomach, intestine, and a tissue pool including esophagus, lung, spleen, heart, and cloacal materials each accumulated ,1% of the initial total 14C residue. The egg follicles in 19 females contained 1 to 23% of the initial total 14C residue, with an average of 10.0 6 9.2% (mean 6 SE, n 5 19). Keywords—Toxicokinetics Oral bioavailability 3,39,4,49,5-pentachlorobiphenyl Northern leopard frogs Rana pipiens