[Pulmonary megakaryocytes (MK) in experimental hemorrhagic shock]

Quantification of MK in blood and pulmonary sections was performed in rabbits with induced hemorrhagic shock (group I) and in control rabbits (group II). In electron transmission microscopy we studied the ultrastructure of pulmonary capillaries. Animals in group I were exsanguinated to achieve systemic blood pressure level of 40 mm Hg. This level was maintained for 1.5 hours and then the rabbits from both groups were sacrificed. Pulmonary arterial and venous blood was sampled in the amount of 10 ml and two sections from each pulmonary lobe were taken. The blood samples were then treated with Streptolysine 0 in order to isolate MK which were counted in the smears. In pulmonary sections MKs were counted per 1 cm2. In animals with shock we found an increase in MKs in the pulmonary artery (means = 4.9 MK/ml against means = 1 MK/ml in venous blood; corresponding values for group II were means = 1.7 MK/ml and 1 MK ml respectively). In the lungs of rabbits in group I we found considerable accumulation of MKs means = 22.4 MK/cm2 (corresponding value for group II means = 2 MK/cm2). It was found that hemorrhagic shock was probably the factor activating the release of MK from the bone marrow to the periferal blood, whereas pulmonary capillaries were an effective filter uptaking circulating MKs. Edematous changes in the capillary endothelium were probably the factors intensifying the process of pulmonary uptake of MK. We discussed the value of pulmonary accumulation of MK in the development of mechanisms leading to adult respiratory distress syndrome.