Tobacco Documents Online

! I I I I I I I I I I I I I I I i I #79 AUTHOR: MEADE, P.D., S. YAMASHIRO, T. HARADA AND R.K. BASUR DATE: 1979 TITLE: INFLUENCE OF VITAMIN A ON THE LARYNGEAL RESPONSE OF HAMSTERS EXPOSED TO CIGARETTE SMOKE CITATION= PROG. EXP TUMOR RES. 24:320-329 (1979) STUDY DESIGN: A study was designed to test whether low levels of vitamin A in the body could hasten the onset of histopathological changes in the larynx generally noted in long term smoke inhalation studies on hamsters. It was also extended to test whether a single administration of vitamin A prior to smoke inhalation offers any protection to laryngeal mucosa against such smoke-related insults. Male Syrian golden hamsters were exposed to smoke from eight Canadian Monitor C cigarettes per day for 6 seeks on an ORNL-Maddox smoke inhalation device. To examine the effects of high levels of vitamin A, two groups of hamsters received a single supplement of either 15,000 or 25,000 IU of retinyl palmitate and then were smoke exposed. Young adult hamsters (6-9 weeks) were fed vitamin A-free diet for 100 days prior to and during exposure to sicarette smoke for 6 weeks to determine whether the low levels would exaggerate the smoke-induced changes and favor the early development of preneoplastic lesions in the larynx. RNDINGSIRESULTS: Histological examination of the larynx in the nonsmoked and smoke-exposed animals revealed that smoke-related changes were most striking the ciliated pseudostratified columnar epithelium near the transitional region in the system of seromucous tubuloalveolar glands. These changes included aggregation of macrophages containing golden-brown pigments, focal hyperplasia, loss of cilia and desquamatlon of the epithelium. The smoke-exposed hamsters also displayed a higher incidence of squamous metaplasia of the surface and glandular epithelium compared to that of sham-smoked and control animals. The histopathological changes in smoke-exposed hamsters supplemented with high levels of vitamin A did not differ significantly from those noted in the group receiving smoke only. Nor did the laryngeal epithelium of the vitamin A supplemented hamsters not exposed to smoke differ histologically from that of the control animals. The liver and plasma vitamin A levels in the supplemented groups were greater than those of hamsters receiving not supplement and the values for the smoke-exposed groups were significantly lower than those of the corresponding groups not exposed to smoke. The highest incidence of squamous metaplasia of the laryngeal and glandular epithelium occurred in smoke-exposed hamsters fed vitamin A-free diet. The frequency of such histopathological changes was higher near the area of transition from stratified squamous to cillated pseudostratified columnar epithelium. No remarkable changes were found in the lower portion of the pharynx. The smoke-exposed hamsters showed lower liver and plasma vitamin A levels than the animals on the vitamin A-free diet not exposed to smoke. CONCLUSIONS= The higher incidence of squamous metaplasia of the laryngeal epithelium noted in the smoke- exposed hamster on a vitamin A-free diet during this study tends to support the hypothesis that vitamin A deficiency results in squamous metaplasia of the epithelium and enhances the bind of PAH to DNA.