Pulmonary neutrophil kinetics in sheep: effects of altered hemodynamics

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Abstract
We investigated the effect of elevated left atrial pressure and reduced cardiac output on pulmonary neutrophil kinetics in the sheep. Sheep neutrophils were isolated, labeled with 111In-oxine, and reinfused. Erythrocytes were labeled with [99mTc]pertechnetate. A gamma camera measured the lung activities of the labeled neutrophils and erythrocytes. The results indicated that 38.5% of the total injected neutrophils marginated in the lung. Pulmonary hemodynamics were altered by inflating a left atrial balloon three times in each sheep for 15–30 min to achieve 5- to 25-mmHg increments in pulmonary arterial wedge pressure. At least a 30-min recovery period was allowed between inflations. After each left atrial balloon inflation, neutrophil uptake remained unchanged from base line, despite decreased mean cardiac output to 0.67 +/- 0.24 (+/- SD) 1/min and increased pulmonary blood volume. The absence of pulmonary neutrophil uptake was confirmed by arterial-venous measurements. Increased pulmonary blood volume had little effect on lung neutrophil uptake, suggesting that most of the pulmonary neutrophils are marginated. We conclude that the lungs have a large marginated neutrophil pool compared with the circulating pool and that reduced cardiac output and elevated left atrial pressure have no effect on pulmonary neutrophil kinetics in the sheep.