Early appearance and localization of intranuclear inclusions in the segments of renal proximal tubules of rats following ingestion of lead.

Intranuclear inclusions in epithelial cells lining rat renal proximal tubules were detected by electron microscopy as early as 4 days after the addition of lead (5 mg/ml as lead acetate) to the drinking water. At 9 and 12 weeks pathological changes, but very few intranuclear inclusions, were apparent in the epithelial cells lining the third segment of the proximal tubules in the outer stripe of outer zone of the medulla. On the other hand, morphological changes were less in the epithelial cells lining the first and second segments of the proximal tubules in the cortex, which contained many intranuclear inclusions. These findings suggest that lead incorporated into the epithelial cells in the proximal tubules may exist in an inert chemical form as inclusions, especially in the second segment. These bodies, therefore, may protect the cells from the toxic effect of lead.