Kinetics of radiolabeled neutrophils in swine

The kinetics of radiolabeled neutrophils (PMNs) as they pass through the lungs of swine were evaluated and compared with those in rabbits (J. Appl. Physiol. 63: 1806-1815, 1987) and dogs (J. Appl. Physiol. 63: 1253-1261, 1987; 65: 1217-1225, 1988) previously reported from our laboratory. 111In-labeled PMNs (111In-PMNs) and 99mTc-labeled erythrocytes were simultaneously injected into the right atrium, and the 111In-PMN percent extraction on the first passage through the lung was determined by the indicator-dilution technique. After 10 min of circulation the distribution of 111In-PMNs in selected organs was determined. The extraction of 111In-PMNs in swine was 88 +/- 3%, which was significantly greater than that of rabbits (78 +/- 3%) or dogs (72 +/- 2%). The recovery of the 111In-PMNs in the lungs of swine was 60 +/- 7%, which was two to three times higher than the recovery in lungs of rabbits or dogs. These results show that radiolabeled PMNs injected intravenously are less able to pass through the pulmonary vasculature and are retained much more within the lung in swine than in rabbits or dogs. This difference could be the result of the presence of pulmonary intravascular macrophages in the lungs of swine.