Transfer of lindane and pentachlorobenzene from mother to newborn rabbits.
After administration of gamma-hexachlorocyclohexane (lindane) (30 mg/kg) to sixteen pregnant rabbits, the transfer and distribution of this insecticide and its metabolite pentachlorobenzene, in foetuses and newborns at the 5th, 10th and 20th days after birth, were investigated. Over one lactation the mothers excreted via the milk about 30% of the lindane present in tissues at the 28th day of pregnancy. The total amount of lindane transferred via milk to 5 day-old newborns was higher than that transferred across the placenta during pregnancy. Lindane concentrations in newborns decreased in spite of the efficient transfer to off-spring by lactating mothers. This cannot be explained by growth alone and indicates that newborns are able to actively metabolize the insecticide. The pentachlorobenzene metabolite produced after lindane administration to the mothers crossed the placental barrier with difficulty during pregnancy, but was readily transferred to off-spring via milk. Pentachlorobenzene levels in neonates increased during lactation by transfer and also as a consequence of endogenous production. At the 20th day of lactation the pentachlorobenzene concentration in maternal and foetal tissues was higher than that of lindane.