Pulmonary lesions in rats caused by intravenous injection

Sprague-Dawley rats in a chronic toxicity test revealed specific pulmonary lesions after 180 days of intravenous injection of samples via the tail vein. Microscopically, thickening of arterial walls, periarteritis, edema of perivascular sheath, arteriosclerosis, vasodilatation, arteriofibrosis, abscess and necrosis of arterial walls, embolism and thrombus of small muscular artery or alveolar capillary, and granulomas sometimes accompanying giant cells were found in the lungs. The emboli consisted of hair of the rats, and granulomas with multinucleated giant cell formation and cellular infiltration were prominent around the emboli. The thrombi was characterized by perivascular cuffing, fibrinous and cellular components. These pulmonary lesions are thought to be caused by hair brought from the tail when intravenous injection was carried out.