Bt. Chen et al., EFFECT OF EXPOSURE MODE ON AMOUNTS OF RADIOLABELED CIGARETTE PARTICLES IN LUNGS AND GASTROINTESTINAL TRACTS OF F344 RATS, Inhalation toxicology, 7(7), 1995, pp. 1095-1108
This study was designed to compare the internal and external depositio
n of cigarette smoke particles in F344/N rats after nose-only or whole
-body exposures and to provide information on how grooming affects the
amount of smoke particles that pass through the gastrointestinal (Gl)
tract. Female rats were exposed to mainstream cigarette smoke by four
different modes: nose-only, tube-restrained (NOT); pelt-only, tube-re
strained (POT); whole-body, tube-restrained (WBT); and whole-body, cag
e-housed (WBC). Groups of rats were exposed simultaneously for 40 min
by 1 of the 4 modes to [C-14]dotriacontane (DTC) labeled cigarette smo
ke at a mean mass concentration of 327 mg/m(3). Half of the rats from
each group were sacrificed immediately after exposure, and the others
were sacrificed 24 h later. Head skin, a sample of subcutaneous fat, G
l tract, trachea/lobar bronchi, lungs, depelted head, depelted carcass
, and remaining pelt were analyzed to determine their C-14 content. Ab
out 60% of the C-14 activity in the respiratory tract in the NOT and W
BT groups was deposited in the pulmonary region, and about 40% was in
the head airways and trachea. The radiolabeled DTC was cleared very sl
owly from the pulmonary region. The initial total body burdens of C-14
in the rats exposed by the WBT and WBC modes were higher than those i
n the rats exposed by the NOT mode as a consequence of pelt contaminat
ion by the C-14-DTC. Grooming resulted in the ingestion of about 80-90
% and 60% of the C-14 activity originally deposited on the head skin a
nd pelt, respectively, by 24 h after exposure. The ratio of the amount
of smoke particles either contained within or passing through the Gl
tract to the amount in lung after 24 h was 2.6 for WBC-exposed rats an
d 1.3 for NOT-exposed rats. We concluded that compared to rats exposed
using the NOT mode, WBC exposures increased the amount of smoke parti
cles passing into the Gl tract by about a factor of two.