Mast cell density in isolated monkey lungs on exposure to cigarette smoke

The density and percentage of degranulated cells of the mast cell population were studied in the isolated lungs of 25 monkeys (Macaca radiata radiata) before and after acute exposure to cigarette smoke. In each animal one lung was used as the test lung while the other lung was used as its control. In the control lungs the total mean mast cell count was 9.5/mm2 and the proportion of degranulated cells was 9.7%. In the lungs exposed to smoke the total counts were lower (7.3/mm2) and the percentage of degranulated cells higher (15.8%). These differences were statistically significant (p less than 0.01) and show that after acute exposure to cigarette smoke there is a degranulation of lung mast cells. Since degranulation is accompanied by local release of histamine, which could act on the smooth muscle of the airways, it is suggested that this may be a mechanism by which smoking-induced acute bronchoconstriction is mediated.