Effect of diet on blood lead concentration in the cynomolgus monkey

Abstract

Infant cynomolgus monkeys ( Macaca fascicularis) were reared from birth in an infant primate nursery and dosed with lead acetate (2 mg Pb/kg body wt/day) from approximately 100 days of age. The monkeys were switched from an infant formula diet to a diet of primate chow and water at 460 days of age. Beginning at approximately 935 days of age, various diets were fed in the following order: infant formula plus a restricted amount of primate chow, infant formula only, infant formula plus cellulose fiber, infant formula plus phytic acid, cow's milk, and primate chow plus water. Blood lead content was determined throughout the experiment. At 360 days of treatment (approx. 460 days of age) the blood lead concentration was 90 μg/dl but decreased to 50 μg/dl within 30 days after the diet was changed to primate chow and water. When the monkeys were 935 days of age the introduction of the infant formula plus a restricted amount of primate chow had little effect on blood lead concentrations. However, when primate chow was removed from the diet so that the monkeys were fed infant formula only, there was a rapid increase in blood lead from approximately 40 to 220 μg/dl. The addition of cellulose fiber to the infant formula had no effect on blood lead concentrations, whereas the addition of phytic acid caused an abrupt decrease to approximately 85 μg/dl. Blood lead concentrations increased to approximately 190 μg/dl when cow's milk only was fed and decreased to approximately 55 μg/dl when the monkeys were returned to a diet of primate chow and water. In a second experiment, infant monkeys were reared as above and dosed from birth with lead acetate at a rate of 25 μg Pb/kg body wt/day. The monkeys were switched to a primate chow and water diet at 200 days of age and at approximately 900 days of age various dietary changes were made that were similar to those described above. Although blood lead concentrations were much lower and more viable than in the 2-mg/kg/day dose group, the data showed a pattern similar to those of the higher dose group.