Leukocytes are required for increased lung microvascular permeability after microembolization in sheep

Area of Science:

• Pulmonary Medicine
• Hematology
• Physiology

Background:

• Microembolization of the pulmonary artery can cause lung injury.
• The role of leukocytes in this process is not fully understood.

Purpose of the Study:

• To investigate the effect of microemboli on transvascular fluid and protein exchange in sheep.
• To determine the role of leukocytes in pulmonary microvascular injury.

Main Methods:

• Sheep were made leukopenic using mechlorethamine hydrochloride and colchicine.
• Pulmonary artery obstruction was induced using glass beads or air bubbles.
• Measurements included pulmonary pressures, cardiac output, lung lymph flow, and lymph protein concentrations.

Main Results:

• Normal sheep developed increased protein-rich lymph flow, indicating increased permeability edema.
• Leukopenic sheep showed a significantly attenuated response to embolization.
• Reduced lymph and protein flow were observed in leukopenic sheep for equivalent obstruction.

Conclusions:

• Circulating leukocytes are essential for microvascular injury in the lungs following microembolization.
• Leukocyte depletion significantly reduces lung permeability edema after pulmonary artery obstruction.