Abstract
OBJECTIVE: To compare the effects of a brief low level exposure to cigarette smoke in rats with known low (Sprague-Dawley) and high (Fisher) airway responsiveness, to test the hypothesis that airways reactivity influences the severity or duration of pulmonary function alterations after cigarette smoke exposure.METHODS: Baseline pulmonary function tests and methacholine dose response tests were conducted in 10 Sprague-Dawley and 10 Fisher rats. On the following day, the animals were reanaesthetized, and breathed for 1 min from a 2 L chamber into which 25 mL of fresh cigarette smoke had been injected, followed by a second set of pulmonary function and methacholine response tests; a final set was performed two weeks later.RESULTS: Sprague-Dawley rats were larger, with larger lung volumes, compliance and flow rates, but Fisher rats showed a fourfold higher airway reactivity. Although neither resistance nor response to methacholine changed in either strain of animal, Sprague-Dawley rats showed an increase in residual volume post smoke, which was not sustained over two weeks, and sustained small increases in vital capacity, total lung capacity and static lung compliance, with a sustained decrease in forced expiratory volume in 0.1 s, while Fisher rats showed only a small sustained increase in functional residual capacity.CONCLUSIONS: Although there are marked differences in pulmonary function between the two different strains of rats, increased airways responsiveness per se does not make the animal more sensitive to the acute effects of cigarette smoke, and the effects of cigarette smoke on pulmonary function are not necessarily related to increased airway resistance. Pulmonary function alterations seen after brief cigarette smoke exposure may be sustained for a relatively long period of time.