Subcellular localization of neptunium-237 in lung and kidney after intratracheal administration in the rat: an ultrastructural and microanalytical study.

Chronic intratracheal administration of 237Np to rate was performed during 6 weeks. The total dose administered was 45.8 kBq. Two methods, electron microscopy and electron probe X-ray microanalysis, were used to determine the intracellular sites of localization of 237Np. Clusters of dense granules were observed in nuclei of pneumocytes and proximal tubular cells of the kidneys. These clusters have been shown to contain neptunium associated with phosphorus, sulfur and calcium. Alterations of nuclei and ultrastructural cytoplasmic lesions were observed. The absorbed doses in lungs and kidneys were very low. These results suggest that the chemical toxicity of 237Np is more important than its radiological toxicity.