Effect of age on the tissue distribution of lead in the rat

The studies described were directed toward the problem of lead intoxication in children. The rat was used as an experimental model. Newborn rats, of the albino Wistar strain, were exposed to lead from birth, first indirectly through mother's milk, then directly through diets containing 0, 0.5, 1.0, or 2.0% lead acetate. By 5 weeks of age the rats receiving lead showed various signs of lead intoxication, ranging from mild growth retardation to a total paralysis of the hindlimbs. The determination of the concentrations of lead in the blood, brain, kidney, and liver revealed that, at 3 and 5 weeks of age, the lead-intoxicated sucking rats had significantly higher concentrations of lead than their mothers. By 7 weeks of age, the concentrations of lead in the blood, kidney, and liver in the young had fallen to concentrations similar to those observed in their mothers. The concentration of lead in the brains of the young animals continued to be consistently higher than that in the mothers. It was concluded that the higher blood and tissue lead concentrations in the young were due to increased gastrointestinal absorption, and the consistently higher brain lead concentrations in the suckling rats were caused by the increased blood lead concentrations and by the fact that lead is not easily removed from the brain.