Role of pulmonary intravascular macrophages activation in increased pulmonary microvascular permeability

Abstract

Pulmonary intravascular macrophages reside in the alveolar capillaries of sheep lung. We tested the effects of pulmonary intravascular mcrophages activation on pulmonary microvascular permeability.
Sheep were divided into 3 groups; latex group, indomethacin group and OKY-046 (thromboxane A2 synthetase inhibitor) group. In each group, we infused latex beads emulsion, 1 μm in diameter, 5.46×10¹⁰ beads/kg, intraarterially. In latex group, lymph protein clearance increased significantly during and after the infusion period. In indomethacin group, increases in lymph protein clearance were blocked completely. However, in OKY-046 group, lymph protein clearance increased significantly 3 hours after the infusion period. In each group, peripheral white blood cell counts decreased significantly during the infusion period, and recovered to the baseline valeus after the infusion. Many latex beads were caught by pulmonary intrvascular macrophages selectively.
These results suggest that pulmonary intravascular macrophages activation through their phagocytic uptake of microparticles is essential to increase in pulmonary microvascular permeability in sheep.