To study effects of cigarette smoke on the cytoplasmic motility (CM) of alveolar macrophages (AM), we measured remanent field strength (RFS) in dogs in vivo. Four days after instillation of ferrimagnetic particles (Fe3O4, 3 mg/kg) into the right lower lobe bronchus, RFS was measured at the body surface immediately after magnetization of the Fe3O4 particles by an externally applied magnetic field. RFS decreased with time due to particle rotation (relaxation), which is thought to be inversely related to CM of AM (J. Appl. Physiol. 55: 1196-1202, 1983). The initial relaxation curve was fitted to an exponential function. The relaxation rate (λ0) increased during cigarette smoke inhalation and returned to base-line values within 15 min. With the inhalation of the smoke of up to five cigarettes, peak λ0 was increased; with a further increase in the number of cigarettes, the effect of cigarette smoke decreased or disappeared. Nicotine injection and acetylcholine inhalation increased respiratory resistance to a degree similar to that observed with cigarette smoke but did not change λ0. However, either substance P (SP) or capsaicin injection increased λ0 in a fashion similar to that noted with cigarette smoke inhalation. Repeated administration of SP produced a significant tachyphylaxis of the effect, and capsaicin did not increase λ0 after the cigarette smoke-induced tachyphylaxis of the effect. Colchicine inhibited the cigarette smoke-induced increase in λ0. These results suggest that cigarette smoke increases CM of AM, probably through the release of tachykinins including SP from sensory nerves in the lung.
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