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[Activated pulmonary intravascular macrophages increase pulmonary microvascular permeability in sheep]
Abstract:
Pulmonary intravascular macrophages (PIMs) reside in the alveolar capillaries of sheep lung. However, the role of PIMs activation in the mechanism of increasing pulmonary microvascular permeability is not clear. We determined, using awake sheep with chronic lung lymph fistulas, the effects of intraarterial infusion of latex beads emulsion (1 microns in diameter) on lung lymph-dynamics. Sheep were divided into 3 groups; control, low dose latex and high dose latex groups. In control group, their lymph-dynamics were stable during the experimental period. In low dose latex group (5.46 x 10(9) beads/kg), lung lymph flow increased during the infusion period, but lung lymph protein clearance did not change. In high dose latex group (5.46 x 10(10) beads/kg), lung lymph flow began to increase during the infusion period and remained high, and lung lymph protein clearance increased significantly during and after the infusion of latex beads emulsion. The latex beads mainly distributed to lungs, and 70% of the beads were caught by PIMs in their phagosomes. These findings suggest that the activation of PIMs through their phagocytic uptake of circulating microparticles increases pulmonary microvascular permeability.
Insights
Pulmonary intravascular macrophages (PIMs) activation by microparticles increases lung microvascular permeability. This study shows PIMs phagocytosis of latex beads elevates lung lymph flow and protein clearance in sheep.
Area of Science:
- Pulmonary physiology
- Immunology
- Microcirculation
Context:
- Pulmonary intravascular macrophages (PIMs) are key immune cells in lung capillaries.
- Their role in regulating pulmonary microvascular permeability is not fully understood.
- Investigating PIMs activation is crucial for understanding lung fluid balance.
Purpose:
- To determine the effect of PIMs activation on pulmonary microvascular permeability.
- To investigate the mechanism by which microparticles influence lung lymph dynamics.
- To elucidate the role of PIMs in response to circulating microparticles.
Summary:
- Sheep infused with latex beads showed dose-dependent increases in lung lymph flow and protein clearance.
- High-dose infusion led to significant increases, indicating enhanced microvascular permeability.
- PIMs phagocytosed 70% of the latex beads, suggesting their activation is central to the observed permeability changes.
Impact:
- This research suggests PIMs activation by microparticle uptake is a mechanism for increasing pulmonary microvascular permeability.
- Findings contribute to understanding inflammatory lung diseases and fluid homeostasis.
- Provides insights into the functional role of PIMs in lung defense and injury.