Background: Vitamin deficiency may be related to carcinogenesis. Cytologic examinations of sputum have already found that the administration of folate and vitamin B12 suppressed the development of squamous metaplasia and atypia in smokers' airways. The authors investigated the effect of folic acid, vitamin B12, and vitamin A on the formation of metaplasia and hyperplasia in methylcholanthrene (MCA)-treated rats.
Methods: The SD strain of rats received 10 mg of MCA intratracheally and was divided into six groups as follows: (1) vitamin A; (2) folic acid; (3) vitamin B12; (4) vitamin B12 with folic acid; (5) a combination of vitamin A, folic acid, and vitamin B12; and (6) no vitamins. The Lower respiratory tract epithelia of the rats were examined histologically 20, 32, and 36 weeks after MCA administration and at the end of the experiment.
Results: A clear difference was detected between the group receiving folic acid and that receiving vitamin A. In the former group, metaplasia was found in only one rat, atypia was not found, and hyperplasia with marked changes was present in less than 50% of other groups. In the latter group, atypia was found in all of the metaplastic foci.
Conclusions: It was suggested that the epithelial hyperplasia and metaplasia of respiratory tract induced by MCA can be suppressed by the administration of folic acid.