Ultrastructural appearances of acute renal papillary lesions induced by aspirin

Renal papillary necrosis develops 16 hr after intravenous administration of aspirin to the uninephrectomised homozygous Gunn rat. Ultrastructural studies show the papillary interstitial cells to be most severely affected, the first changes being visible at 1 hr. Changes in capillaries are late in onset, and this suggests that the lesions are due to a direct toxic effect rather than to ischaemia.