Related Experiment Videos
Marginated pool of neutrophils in rabbit lungs
C M Doerschuk1, M F Allard, B A Martin
1University of British Columbia, Pulmonary Research Laboratory, Vancouver, Canada.
Abstract:
The size and location of the marginated pool of neutrophils (PMNs) in rabbit lungs were evaluated, and the rate of exchange of the PMNs with the circulating pool was determined. 99mTc-labeled erythrocytes (99mTc-RBCs) and 125I-labeled macroaggregated albumin (125I-MAA) were used to determine RBC transit times in the pulmonary circulation. Radiolabeled PMNs were studied on their first passage through the lungs. After 10 min of circulation, the lungs were fixed, gamma counted, and prepared for morphometric and autoradiographic studies; 74 +/- 3% of the PMNs was retained in the lungs on the first passage, and 23 +/- 2% was within the pulmonary marginated pool 10 min later. The regional PMN retention and the rate of exchange between the marginated and circulating PMN pools in the lung were directly related to RBC transit time. The radiolabeled PMNs distributed similarly to the unlabeled cells within the microvasculature and had a similar exchange rate between the marginated and circulating pools (1.4 +/- 0.2%/s using labeled cells and 1.5 +/- 0.5%/s using unlabeled cells). The marginated pool was located primarily within alveolar capillaries and contained two to three times as many PMNs as the total circulating pool.
Insights
Rabbit lungs retain 74% of neutrophils (PMNs) on first passage, with most forming a marginated pool in alveolar capillaries. This pool
Area of Science:
- Pulmonary physiology
- Hematology
- Immunology
Background:
- Neutrophils (PMNs) play a critical role in lung immunity and inflammation.
- Understanding the dynamics of PMNs within the pulmonary circulation is essential for diagnosing and treating lung diseases.
Purpose of the Study:
- To determine the size and location of the marginated pool of neutrophils (PMNs) in rabbit lungs.
- To quantify the rate of exchange between marginated and circulating PMN pools in the pulmonary vasculature.
Main Methods:
- Utilized 99mTc-labeled erythrocytes (99mTc-RBCs) and 125I-labeled macroaggregated albumin (125I-MAA) to assess RBC transit times.
- Studied radiolabeled PMNs during their first passage through the lungs.
- Conducted morphometric and autoradiographic analyses of lung tissue after 10 minutes of circulation.
Main Results:
- 74% ± 3% of injected PMNs were retained in the lungs during the first passage.
- 23% ± 2% of PMNs were found within the pulmonary marginated pool 10 minutes post-injection.
- PMN retention and exchange rates correlated with red blood cell (RBC) transit times.
- The marginated pool, primarily in alveolar capillaries, was 2-3 times larger than the circulating pool.
Conclusions:
- The rabbit lung marginated pool of neutrophils is substantial and primarily resides in alveolar capillaries.
- PMN dynamics within the lung are influenced by vascular transit times.
- The marginated pool exchanges with the circulating pool at a consistent rate, comparable between labeled and unlabeled PMNs.