Pathology of experimental pulmonary bone marrow embolism. I. Initial lesions of the rabbit lung after intravenous infusion of allogeneic bone marrow with special reference to its pathogenesis.

In order to investigate the initial lesions of pulmonary bone marrow embolism and its pathogenesis, the author studied the pulmonary changes of 70 rabbits during a 24-hour period after the infusion of 500 mg of fresh allogeneic bone marrow into the marginal ear veins. After 30 minutes, leukostasis was observed in the non-embolized small arteries. After 2 hours, leukostasis increased and by 5 to 10 hours, it reached a maximum, still decreased considerably after 24 hours. In the perivascular connective tissue, edema and inflammatory cell infiltration had occurred as a result of increased vascular permeability due to leukostasis. Fifteen minutes after intravenous administration of a single shot of indomethacin (5 mg/kg), the infusion of allogeneic bone marrow was performed. Five hours after the infusion, the suppression of pulmonary vascular leukostasis and interstitial edema were observed. The effect of drugs on morphological changes, however, is extremely small in the group pre-treated with diphenhydramine hydrochloride (3 mg/kg). The author concluded that the mechanical injury of vascular endothelial cells by emboli and the accumulation of leukocytes in the pulmonary vessels may play an important role in the pathogenesis of the initial change of pulmonary bone marrow embolism. It is also suggested that the embolized bone marrow in the small arteries and vasculitis may lead to arteriosclerosis in the future.