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.

In a controlled experiment, 6 groups of SPF rats were given cigarette smoke condensate (SWS) in solid form without a vehicle once fortnightly by intratracheal instillation, at 3 dose levels with or without additional exposure to the vapour phase of smoke (VP) from 10 plain cigarettes each week. Treatment continued for life. Six other groups were similarly treated with one of 3 fractions of condensate with or without VP. Exposure to VP was associated with a significant reduction in body weight, but not signficantly with the incidence or severity of any observed pathological change in the lungs. A significant dose-related assoication was seen between SWS or its fractions and the incidence and degree of chronic respiratory disease (CRD), cuboidal or columnar metaplasia (CCM) and squamous metaplasia of alveolar epithelium (Sq.M) produced. No neoplasms, however, were elicited. A significant correlation was found between the degrees of CCM and of Sq.M produced in the 24 groups exposed to SWS or fractions. The results are discussed in the light of studies in which rats were exposed to tobacco smoke by inhalation and of studies in which the same condensate and fractions were applied to mouse skin.