RESPONSE OF PULMONARY (CIRCULATING) MEGAKARYOCYTES TO EXPERIMENTALLY INDUCED CONSUMPTION COAGULOPATHY IN RABBITS

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Abstract
The effects of slow temporary infusion of a tissue thromboplastin solution into the superior vena cava on pulmonary and circulating megakaryocytes were studied in 40 rabbits (2-48 h after infusion) and related to 6 noninfused and 7 infused with normal saline. This is a simple and specific method of inducing a fall in blood platelet levels and thereby an activation of thrombocytopoiesis and megakaryocytopoiesis. The induced intravascular coagulation is probably counterbalanced by an activated fibrinolysis allowing the animals to survive the infusion and thereby offering the possibility of studying the long-term effects. An increase to about 300% of the normal values in circulating and pulmonary megakaryocytes was found 20 and 24 h after the onset of the infusions, respectively. The number of circulating and pulmonary megakaryocytes, showing great individual variations, dropped to normal levels within 28 h after onset of the infusions, which means that megakaryocytes remain detectable for less than 8 h in the lungs. No increase was found in pulmonary megakaryocytes in the control (saline infused) group. The entrance of megakaryocytes from the bone marrow into the blood circulation is apparently an incidental event, the number in the circulation reflecting the activity of megakaryocytopoiesis. Intravascular coagulation may be 1 of the major pathophysiological mechanisms leading to an increase in pulmonary megakaryocytes.