Residual pulmonary neutrophils are involved in vaso- and bronchoconstrictor responses to platelet activating factor in the isolated buffer-perfused rat lung

The aim of the study was to quantify residual neutrophils sequestrated in the isolated rat lung, perfused at a constant flow with Krebs-Hanseleit solution, and to analyze their possible influence on functional responses of the isolated lung. For that purpose we assessed neutrophil content in the isolated lung as well as in the effluent from the lung using an assay of myeloperoxidase (MPO) activity. We showed that a considerable pool of neutrophils remained in the isolated lung even after a 20-min period of washout with buffer solution. Moreover, these residual neutrophils were responsible for platelet activating factor (PAF)-induced vaso- and bronchoconstriction but not for oedema formation. We conclude that when studying responses to pharmacological agents in isolated buffer-perfused lung, the presence of sequestrated neutrophils should be taken into account.