Mainstream and sidestream cigarette smoke exposure increases retinol in guinea pig lungs

We have studied in guinea pigs the effects of cigarette smoke exposure on vitamin A (retinol) levels in plasma, lung, lung lavage, and liver. Smoke was generated from 1R3F cigarettes in a smoke exposure instrument designed by University of Kentucky Tobacco and Health Research Institute. Three-week-old male guinea pigs were exposed to mainstream, sidestream, or sham smoke, generated twice daily from three cigarettes for 6 weeks. In addition, some animals were kept as room controls for some time. After 6 weeks of smoke exposure, some animals were allowed to recover for 6 weeks without smoke. After 6 weeks of smoking, the plasma retinol levels were lower in both smoke exposed groups when compared to the values in the sham group. Furthermore, in comparison to the sham group, the mainstream and sidestream smoke exposed groups showed a 7.6- and 8.3-fold increase in the levels of lung retinol, respectively. After the 6-week recovery period, plasma retinol of both smoke-exposed groups reached the control levels. In contrast, withdrawal of smoking did not show such an effect on the lung retinol level in both mainstream or sidestream groups. Electronmicroscopy of the lungs showed deleterious alterations in the morphology of the lungs in both mainstream and sidestream groups. Although the mechanism(s) involved in the elevation of retinol content of the lung due to smoke exposure remains to be elucidated, it is of interest that elevation of retinol content and alteration of lung morphology occurred not only in the mainstream smoke exposed but also in the sidestream group.