Oral bioavailability and toxicokinetics of 3,3 ',4,4 ',5-pentachlorobiphenyl in northern leopard frogs, Rana pipiens

This study is the first report on oral bioavailability, whole-body eliminat ion, and distribution of a specific polychlorinated biphenyl (PCB) congener on an amphibian species, northern leopard frogs. Each frog was orally dose d once with either 0.35 or 5.0 mg/kg PCB 126 (based on frog wet wt), includ ing tracer C-14-PCB 126 (3',4',5'-phenyl-ring-C-14) by force feeding it a c ricket injected with the PCB. We found no statistical difference (t = 0.917 , df = 5, p = 0.401) in the average 48-h oral bioavailabilities of 0.35- an d 5.0-mg/kg dosage groups, which were 84.6 +/- 5.8% (mean +/- SE, n = 4) an d 90.9 +/- 1.5% (n = 3), respectively. Statistical analysis indicated that time was the only independent variable affecting the retention of whole-bod y C-14 content. Kinetics were apparently first order because elimination ra te was independent of dose. Assuming a single pool and one elimination rate , the t(1/2) value for whole-body elimination of PCB-derived C-14 was 763 d . Liver, fat bodies (corpora adiposa), carcass (head, bone, cartilage mater ials, and residues of other tissues), skin, and muscle were the major organ s for PCB 126 retention in both dosage groups. The concentrations of C-14 r esidue in fat bodies were relatively constant throughout the experiment. Ho wever, total residues in fat bodies declined throughout the experiment in b oth 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 to tal C-14 residue. The egg follicles in 19 females contained 1 to 23% of the initial total 14C residue, with an average of 10.0 +/- 9.2% (mean +/- SE, n = 19).