EFFECTS OF PRENATAL AND POSTNATAL EXPOSURE TO 3,3',4,4',5-PENTACHLOROBIPHENYL ON PHYSICAL DEVELOPMENT, NEUROBEHAVIOR AND XENOBIOTIC-METABOLIZING ENZYMES IN RATS

An experiment was conducted to study the effects of the coplanar non-o rtho-chlorinated congener 3,3',4,4',5-pentachlorobiphenyl (PCB-126) in rats exposed during fetal development and postnatal suckling period. Two groups of eight dams were administered by gavage six doses of 10 a nd 20 mu g/kg body weight of PCB-126 dissolved in corn oil every secon d day from days 9 to 19 of gestation. The corresponding control rats w ere treated with corn oil only. The physical development of the offspr ing was observed. From age 5 to 18 weeks, 12 randomly selected pups fr om each group were tested daily for visual discrimination with success ively more demanding tasks in Skinner boxes. The effects of PCB-126 on hepatic xenobiotic metabolizing enzyme activities and the concentrati ons of PCB in the liver and brain were investigated in samples from pu ps of different age and from their mothers. The litter size, the body weights, and the survival of the exposed suckling were reduced, and th e onset of spontaneous movement and neuromuscular maturation were dela yed, whereas the development of reflexes was not affected, as compared to controls. The body weight was still reduced in a dose-related mann er up to 18 weeks postpartum. Also, the postpartum body weight of the PCB-exposed mothers was reduced as compared to controls, but the diffe rence disappeared at weaning. The hepatic enzyme activities of cytochr ome P450 1A1 examined by ethoxyresorufin O-deethylase (EROD) and gluta thione S-transferase (GST) toward 1-chloro-2,4-dinitrobenzene (CDNB) w ere increased in both the exposed pups and their mothers, and the rela tive liver weight wa increased in the exposed pups. The behavior train ing in Skinner boxes did not reveal PCB effects on the learning perfor mance or the activity level. Hepatic PCB-126 residues were detected in samples collected throughout the experiment, whereas no detectable co ncentration was found in the brain. We conclude that exposure of this PCB congener in utero and through lactation showed fetotoxic effects, delayed physical maturation, and induced liver xenobiotic metabolizing enzymes without causing neurobehavioral effects.