The Pulmonary Vessels as a Filter for Circulating Megakaryocytes in Rats

Investigations in rats comparing the inferior vena cava and the aorta with respect to the number of megakaryocytes (MK) in the blood have shown that pulmonary circulation plays an effective role in filtering circulating MK. Large numbers of retained MK showing degenerative nuclear changes may be recovered by retrograde perfusion of the lungs, while only a few are pressed by the blood stream to the left atrium. A significantly higher blood platelet count in the aorta than in the inferior vena cava suggests platelet release from retained MK.