Phenoclor DP5 (DP5), a mixture of
polychlorinated biphenyls (
PCBs), was administered to lactating rat dams, every two days from postnatal days 2 to 20, at 50 mg/kg of
body weight. Resulting effects on tissue concentrations of
PCBs and on liver
lipids,
nucleic acids (
DNA and
RNA),
proteins and blood
lipids of offspring, at different times after weaning, until postnatal day 100, were studied. On postnatal day 21, DP5 contents found in liver, brain and fat of young rats indicated that a great part of the dam's body stores of
PCBs was eliminated into the milk. These accumulations were related to an increase of relative liver weight, a decrease in
DNA concentration and a rise in liver
RNA,
protein and
phospholipid levels, indicating an inducing effect of DP5 in weanling rat. Changes in lipid metabolism were associated with increases of liver
triacylglycerol and
cholesterol and decrease of blood
triacylglycerol. Both sexes exhibited an identical responsiveness to
PCBs. The biochemical alterations observed in liver and blood at weaning, disappeared with time and were no longer detectable after postnatal day 40 in both sexes. Relative liver weight increase persisted until postnatal day 60 in males and postnatal day 100 in females. Residual aspects of alterations induced before weaning, by exposure via milk, could persist until postnatal day 100. Permanent effects of
PCBs, after perinatal exposure could be assessed in later life of rats, when
PCBs were almost completely cleared from body tissues.