Ferritin in rat kidneys with specific lesions due to a single dose of lead

In the proximal tubular cells of rats or mice given a single, parenteral dose of lead, clusters of ferritin are frequently associated with characteristic cytoplasmic fibrillar bodies. To learn more about this relationship, the authors have investigated content and synthesis of ferritin protein and incorporation of iron into ferritin in rat kidneys 48 hours after a single parenteral dose of lead (10 μg/g). By immunoradiometric assays, they found that the kidneys of female rats, whether treated with lead or not, contained significantly more ferritin protein than did kidneys of males of the same age and provenance. Administration of lead diminished (or did not significantly alter) the incorporation of ¹⁴C-amino acids into newly synthesized ferritin protein. Contrary to expectation, administration of lead tended to depress incorporation of ⁵⁹Fe into kidney ferritin in rats maintained on standard rations and distilled water. Electron microscopy confirmed the presence of clusters of ferritin in close association with dense fibrillar bodies in the cytoplasm of proximal tubular cells of rats given lead. Considered together, the findings indicate that clustering of ferritin next to the dense fibrillar cytoplasmic lesions is a selective effect of lead that requires neither augmented synthesis of ferritin protein nor increased incorporation of iron into preexisting ferritin.