In vitro hepatic enzyme activity in rats exposed nose-only to cigarette smoke.

Adult male Sprague-Dawley rats were exposed nose-only to cigarette smoke for 10 or 20 min/day for up to 17 weeks. Other animals, identified as sham controls, were handled identically except that cigarettes were not placed in the smoking apparatus. A series of in vitro assays were used to monitor the effects of cigarette smoke and stress on hepatic S15 enzyme activities. Smoke exposure had no effect on any of the biotransformation pathways beyond that resulting from stress associated with the smoke procedure. However, smoking did significantly reduce hepatic levels of glutathione after 16 and 17 weeks of exposure. Smoking also caused a dramatic reduction in weight gain over the various exposure periods. This same effect, but to a lesser degree, was also noted in the sham control animals. These results demonstrate the definite need to reduce the obvious trauma caused by restraining rats for forced, nose-only exposure to the smoke. Until this is accomplished, results of studies on the influence of smoking on rat biochemistry and physiology will be difficult to properly interpret.