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-ortho-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 and 20 mu g/kg body weight of PCB-126 dissolved in corn oil every second day from days 9 to 19 of gestation. The corresponding control rats were treated with corn oil only. The physical development of the offspring was observed. From age 5 to 18 weeks, 12 randomly selected pups from each group were tested daily for visual discrimination with successively more demanding tasks in Skinner boxes. The effects of PCB-126 on hepatic xenobiotic metabolizing enzyme activities and the concentrations of PCB in the liver and brain were investigated in samples from pups of different age and from their mothers. The litter size, the body weights, and the survival of the exposed suckling were reduced, and the onset of spontaneous movement and neuromuscular maturation were delayed, whereas the development of reflexes was not affected, as compared to controls. The body weight was still reduced in a dose-related manner up to 18 weeks postpartum. Also, the postpartum body weight of the PCB-exposed mothers was reduced as compared to controls, but the difference disappeared at weaning. The hepatic enzyme activities of cytochrome P450 1A1 examined by ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) toward 1-chloro-2,4-dinitrobenzene (CDNB) were increased in both the exposed pups and their mothers, and the relative liver weight wa increased in the exposed pups. The behavior training in Skinner boxes did not reveal PCB effects on the learning performance or the activity level. Hepatic PCB-126 residues were detected in samples collected throughout the experiment, whereas no detectable concentration 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.