Dosimetry and cardiopulmonary function in rats chronically exposed to cigarette smoke

Abstract

Groups of 80 female F-344 rats were exposed, in Maddox-ORNL smoking machines, to smoke from three types of research cigarettes: high tar, low nicotine (HT-LN, code 13 as provided by the National Cancer Institute); low tar, high nicotine (LT-HN, code 27); and high tar, high nicotine (HT-HN, code 32). Rats were exposed to approximately 10 puffs of cigarette smoke during each of eight daily exposure sessions, 7 days/week for 24 months. Additional groups were sham-exposed on the same schedule, or served as untreated “shelf” controls. Heart rate and breathing pattern (tidal volume, respiration rate, and minute volume) were measured both during exposure and while the animals were not exposed to smoke. During exposure, smoke-exposed rats inhaled 75% less air and had 40% lower heart rates than sham-exposed rats. Results were similar for all smoke-exposed groups, and differences between sham- and smoke-exposed groups persisted throughout the 24-month exposure. When not being exposed, heart rate and breathing pattern were also different between smoke- and sham-exposed groups; tidal volumes were higher and respiration and heart rates were lower in smoke-exposed than in sham-exposed animals. In general, these differences between smoke- and sham-exposed groups developed during the first 12 months of exposure and diminished thereafter. Of the smoke-exposed groups, rats exposed to LT-HN cigarettes showed the greatest changes, and rats exposed to HT-LN cigarettes showed the least changes, in heart rate and breathing patterns. Arterial blood pressure was consistently higher in smoke-exposed than in sham-exposed animals following 18 and 24 months of exposure. This study showed that cardiopulmonary function in rats was significantly affected by chronic cigarette-smoke exposure.