Effects of neutrophils on collateral ventilation and peripheral lung reactivity in dogs

We studied the effects of neutrophil activation on collateral ventilation and peripheral lung reactivity in anesthetized dogs. A fiberoptic bronchoscope was wedged into a segmental airway under direct vision. Ventilation beyond the obstruction thus occurred only through collateral channels. Through one lumen of a double-lumen catheter threaded through the suction port of a bronchoscope, 5% CO2 in air was infused at a known constant rate (V coll). Through the other lumen, pressure at the tip of the bronchoscope was monitored (Pb). For measurements of resistance to flow through the collateral system (Rcs), the ventilation was stopped at functional residual capacity (FRC). Histamine was delivered through the bronchoscope to the obstructed lung segment in the form of an aerosol mist generated by an ultrasonic nebulizer. Measurements of Rcs were used as a parameter of the peripheral lung reactivity to histamine challenge. Within one hour after intravenous infusion of phorbol myristate acetate (PMA), a neutrophil activator, the reactivity to histamine significantly increased. After this, Rcs increased even without histamine challenge. This increase may have been due to an edematous injury of lung caused by PMA. The nature of the injury was confirmed by wet to dry weight ratios. In the other group, the white cell count dropped below 1000 per cu. mm. after intravenous infusion of nitrogen mustard. The same experimental protocols were followed. The Rcs did not increase even with histamine challenge. Our results suggested that substances such as oxygen radicals and arachidonic acid metabolites, which can be released by activated neutrophils, may not not only increase peripheral lung reactivity, but may also induce pulmonary edema.