Subchronic lead feeding study in male rats and micropigs

This study compared the lead uptake from contaminated test soil of known lead concentration with a soluble lead acetate standard, which was considered to be 100% bioavailable. This study also compared the lead bioavailability from this lead-contaminated soil between rats and micropigs. Harlan Sprague-Dawley rats and Yucatan micropigs were fed lead-contaminated soil as a 5% (w/w) mixture with their diet. The lead-contaminated soil was either a specific test soil of known lead concentration (1000 microg/g) or basal low concentration lead soil ( approximately 135 microg/g), which was spiked with lead acetate to match the lead content of the test soil. The effective diet lead concentration was 50 microg Pb/g diet. Results demonstrated that rats reached steady-state concentrations of blood lead by week 2, whereas micropigs did not reach steady state until week 4. In addition, final blood lead concentrations in micropigs were four-fold higher than those in rats. In the micropigs, the final blood lead levels in the test soil study group were significantly lower than those in the lead acetate study group, although there was no significant difference between study groups in the rats. Tissue lead concentrations were significantly higher in micropigs than those in the rats, although the diet lead concentrations in both sets of animals were the same. In summary, because of the greater sensitivity in demonstrating higher tissue lead incorporation in micropigs as compared to rats, the micropig is a better animal model for demonstrating the differences in relative lead bioavailability when testing different sources of lead-contaminated soils.