Acetic acid exposure: Animals were exposed to acetic acid by having them inhale a nebulized solution of acetic acid for 2 mins, using the same delivery method. The nebulizer was changed, and the plastic box was thoroughly flushed immediately following the acid exposure. An 8 N acetic acid solution was chosen based on preliminary experiments. Inhalation of 8 N acetic acid caused a transient increase in Rl and El (Figure 2). Lower concentrations (2 to 4 N) did not cause a significant postexposure increase in Rl, whereas inhalation of a 13 N solution was lethal. birth control pills
Study groups and follow-up protocol: Eleven animals (study group) were exposed to 8 N acetic acid, as previously described. Three rats were given saline inhalation (control group). RL was measured before the acetic acid exposure and at 1, 5, 15 and 30 mins postexposure. Airway responsiveness (Mch challenge) was conducted at baseline (day B) and repeated 24 h (day 1) and one week (day 7) postexposure. Statistical analysis: Group results are expressed as means ± SE, except for EC200RL values, which are reported as geometric means. The significance of the difference between means was evaluated using ANOVA with Tukey’s honestly significantly different post hoc comparison. EC200RL data were log transformed before ANOVA. Significance was considered to be established when P<0.05.
Figure 2) Postexposure lung resistance ratio normalized to baseline postsaline inhalation value (Rl/Rs) following the inhalation of three different acetic acid concentrations. Each line represents a single animal. Addition of 8 N acetic acid caused a transient (70%) increase in Rl/Rs