Hs. Sekhon et al., CIGARETTE-SMOKE CAUSES RAPID CELL-PROLIFERATION IN SMALL AIRWAYS AND ASSOCIATED PULMONARY-ARTERIES, American journal of physiology. Lung cellular and molecular physiology, 11(5), 1994, pp. 557-563
To determine whether smoke could directly affect the cells of the smal
l airways and the small vessels, we exposed Sprague-Dawley rats to the
whole smoke of 7 cigarettes/day for 1, 2, or 7 days. Three hours befo
re the rats were killed, 5-bromo-2'-deoxyuridine (BrdU) was administer
ed. Labeled nuclei were counted in histological sections stained with
antibodies to BrdU. In smokers, pulmonary artery walls at the level of
the membranous bronchioles (MB), respiratory bronchioles (RB), and al
veolar ducts (AD) showed significant increases in labeled nuclei at al
l three times; increases in endothelial labeling were only present in
vessels associated with AD. Significantly increased labeling was also
seen in the epithelium and walls of MB and RB themselves at all time p
eriods. However, there was no correlation between labeling indexes in
matched pairs of airways and vessels. Smoke had no effect on the label
ing of mesothelial and submesothelial cells. We conclude that cigarett
e smoke rapidly causes proliferation of intrinsic cells in the airways
and small vessels; this effect may lead eventually to airway wall mus
cular hyperplasia and fibrosis (small airways disease) and to vascular
changes associated with pulmonary hypertension. However, the lack of
correlation between labeling indexes in the vessels and airways sugges
ts that different mediators are involved at these two sites. At least
over the time course of this experiment, smoke does not cause prolifer
ation of mesothelial or submesothelial cells.