Response of rat lung to inhaled vapour phase constituents (VP) of tobacco smoke alone or in conjunction with smoke condensate or fractions of smoke condensate given by intratracheal instillation

Pulmonary macrophage mobilization in hamsters after cessation of smoking

Male Syrian hamsters were exposed to smoke from three different types of cigarettes rated as mild, medium, and strong on the basis of their smoke chemistry for 4 weeks. These hamsters were euthanized at 0, 1 and 2 weeks of recovery after the last smoke exposure to study the pulmonary cell response after cessation of smoking. The free macrophage count determined on lung sections stained with hematoxylin and eosin was used as the index to evaluate the rate of recovery from smoke-related insult caused by the different types of cigarettes. The number of macrophages in the smoke-exposed hamsters was consistently greater throughout the recovery period than in the controls, depending on the amount of particulate components including tar and nicotine in the test cigarettes. The macrophage mobilization peaked at the first week of recovery and then showed a tendency to decrease at the second week. At the second week, however, the hamsters exposed to smoke from strong or medium cigarettes still showed significantly higher counts than the controls, while no significant change was noted in those exposed to smoke from mild cigarettes. These results indicate that the process and duration of recovery after cessation of smoking may depend on the extent of particulate matter impinging on the respiratory tract, so that strong cigarettes would be more hazardous because of greater number and longer retention of macrophages in the lung.

Deposition and clearance of labeled cigarette smoke particles in rat respiratory and digestive tract

In this investigation 160 8-wk-old Sprague-Dawley rats inhaled smoke from 14C-labeled cigarettes in a Hamburg II smoking machine. The research cigarettes were labeled with [16,17-14C]dotriacontane. Eighty of the rats were acclimatized to smoke from nonlabeled research cigarettes for 21 d before inhaling labeled cigarette smoke. The investigation was divided into four experiments. In experiment I all rats were killed immediately after exposure to the 14C-labeled smoke from 30 cigarettes (10 muCi per cigarette) and the organs of the respiratory and digestive tracts were measured for 14C activity. These animals showed high activity in the apex nasi, fundus nasi, and larynx. The highest activity was found in the lobus dexter caudalis and the lobus sinister of the lung. The lungs contained four-fifths of the condensate inhaled into the respiratory tract. In experiment II three animals were killed immediately after smoking, three after 6 h, and four after 24 h. No activity was found after 6 h in apex, fundus nasi, larynx, and trachea. The lungs showed no clearance at all. The activity in the digestive tract was highest in the stomach and the esophagus immediately after cessation of smoking. These values decreased rapidly after 6 h. In experiment III the animals were killed after 7, 21, and 42 d. Clearance from the upper respiratory tract was fast, whereas clearance from the lungs was slow. Clearance from all lung lobes was faster in the nonacclimatized animals. In experiment IV the rats inhaled the smoke from 14C-labeled cigarettes (2 muCi per cigarette) on 5 successive days. The animals were killed 7, 14, and 21 d after the last smoke inhalation. Clearance from the lungs was slower in acclimatized and non-acclimatized animals than in experiment III.

Inhalation toxicity studies on cigarette smoke. IV. Expression of the dose of smoke particulate material applied to the lungs of experimental animals

Calculations of total particulate matter (TPM) dose applied to the lungs of animals are made from experimental dosimetry data. TPM dose levels achieved in a number of species following exposure to smoke are related to body weight, lung weight and alveolar surface areas of these animals. The dosage levels achieved in animals are compared with estimate of TPM dose retained by a smoker. Cigarette dosage equivalents to which animals are subjected can be calculated on the basis of these comparisons. The validity of making such extrapolations from animal dosimetry data to the human exposure situation is discussed.

Response of rat lung to inhaled tobacco smoke with or without prior exposure to 3,4-benzpyrene (BP) given by intratracheal instillation

SPF rats were exposed to the smoke from 10 cigarettes per week from the age of 10 weeks until they died. Survival, body weight, tumour incidence and histopathological appearances of the lungs were compared with those for untreated sham exposed rats. Two further groups were given a single dose of 3,4-benzyprene (BP) by intratracheal instillation. One of these was then exposed to the smoke of 10 cigarettes per week till death. Compared with untreated or sham exposed rats, exposure to smoke was associated with a significant reduction in incidence of mammary tumours. Exposure to smoke was associated with an increasing incidence of collections of macrophages laden with golden-brown pigment (GBM) and of areas of cuboidal or columnar metaplasia (CCM) or squamous metaplasia (Sq.M) of alveolar epithelium. In control rats there was virtually no GBM, a low incidence of CCM and Sq.M. Four out of 406 smoke exposed rats which came to post mortem had squamous neoplasms in the lungs, 3 having lesions of doubtful malignancy and one having a squamous carcinoma. In contrast, no squamous neoplasms were seen in 197 control rats. This difference was not statistically significant. The findings in rats given a single dose of BP were, in all the above respects, similar to those in untreated rats, except that one developed a squamous carcinoma of the lung. The effects of a single dose of BP followed by smoke exposure were in general similar to those of smoke exposure only. Three rats on this treatment regimen developed squamous cancers of the lung. None of the treatments increased the incidence of adenomata of the lungs. The results are discussed in relation to other studies of the effects of smoke exposure on rats and other species.

Response of rat lung to tobacco smoke condensate or fractions derived from it administered repeatedly by intratracheal instillation

The repeated intratracheal instillation of cigarette smoke condensate (SWS) in rats at close to maximum tolerated dose levels failed to induce squamous neoplasms in the lungs although such treatment was associated with an increased incidence of cuboidal/columnar metaplasia (CCM) and squamous metaplasia (Sq.M) of alveolar epithelium. With one exception, various fractions of SWS had no effect on lung tumour incidence though some were more effective than SWS in increasing the incidence of CCM and Sq.M. The exceptional fraction, Fraction P, which contains most of the polycyclic aromatic hydrocarbons of smoke and is the most effective of the fractions tested in producing tumours in mouse skin, gave rise to 4 squamous tumours of doubtful malignancy and one metastasizing squanmous carcinoma among 3 groups of 18 animals exposed at 3 different dose levels. The results are discussed in relation to the possible development of a method for comparing condensates for relative lung carcinogenicity.

Response of rat lung to 3,4-benzpyrene administered by intratracheal instillation in infusine with or without carbon black

In a controlled experiment groups of SPF Wistar rats were give 18 once-fortnightly doses of 0-5, 1-0 or 2-0 mg 3,4-benzpyrene (BP) suspended in infusine (I) or in carbon black (CB) + I by intratracheal instillation. Of rats examined post mortem, 1/16 given I+CB only, 0/16 given I only, 15/51 given BP in I+CB and 24/48 given BP in I developed squamous neoplasms of the lung. The incidence of tumours was significantly related to dose of BP. At the 1 or 2 mg dose levels BP in I only was more productive of tumours than BP in I+CB. Other changes encountered included squamous metaplasia of alveolar and bronchiolar epithelium (Sq.M), but not of bronchial epithelium, and cuboidal and columnar metaplasia of alveolar epithelium in the vicinity of terminal bronchioles (CCM). Sq.M was associated with exposure to BP or I+CB. CCM was strongly associated with exposure to I+CB but only weakly with exposure to BP.