DEVELOPMENTAL TOXICITY OF PCB-126 (3,3',4,4',5-PENTACHLOROBIPHENYL) IN NESTLING AMERICAN KESTRELS (FALCO-SPARVERIUS)

Planar PCB congeners are embryotoxic and teratogenic to birds includin g American kestrels. The developmental toxicity of 3,3',4,4',5-pentach lorobiphenyl (PCB 126) was studied in the posthatching kestrel as a mo del for the eagle. Nestlings were dosed orally for 10 days with 5 mu l /g body weight of corn oil (controls) or the planar PCB 126 at concent rations of 50, 250, or 1000 ng/g body weight. Dosing with 50 ng/g of P CB 126 resulted in a hepatic concentration of 156 ng/g wet weight, liv er enlargement and mild coagulative necrosis, over 10-fold increases i n hepatic microsomal ethoxyresorufin-O-dealkylase and benzyloxyresoruf in-O-dealkylase, and approximately a 5-fold increase in methoxyresoruf in-O-dealkylase. At this dose, mild to moderate lymphoid depletion of the spleen was apparent, as were decreased follicle size and content o f the thyroid. At 250 ng/g, concentration of PCB 126 in the liver was 380 ng/g with increasing multifocal coagulative necrosis, decreased bo ne growth, decreased spleen weight with lymphocyte depletion of the sp leen and bursa, and degenerative lesions of the thyroid. At 1000 ng/g, the liver concentration was 1098 ng/g, accompanied by decreased bursa weight, decreased hepatic thiol concentration, and increased plasma e nzyme activities (ALT, AST, and LDH-L) in addition to the previous eff ects. Highly significant positive correlations were noted between live r concentrations of PCB 126 and the ratio of oxidized to reduced gluta thone. These findings indicate that nestling kestrels are more suscept ible to PCB 126 toxicity than adults, but less sensitive than embryos, and that planar PCBs are of potential hazard to nestling birds. (C) 1 996 Society of Toxicology.