Tracheobronchial epithelium has been a focus of intense investigation in the field of chemical
carcinogenesis. We have reviewed some biochemical investigations that have evolved through linkage with
carcinogenesis research. These areas of investigation have included kinetics of
carcinogen metabolism, identification of
carcinogen metabolites, levels of
carcinogen binding to
DNA, and analysis of
carcinogen-
DNA adducts. Such studies appear to have provided a reasonable explanation for the susceptibilities of the respiratory tracts of rats and hamsters to
carcinogenesis by
benzo(a)pyrene. Coinciding with the attempts to understand the initiation of
carcinogenesis in the respiratory tract has also been a major thrust aimed at effecting its prevention both in humans and in animal models for human
bronchogenic carcinoma. These studies have concerned the effects of derivatives of
vitamin A (
retinoids) and their influence on normal cell biology and biochemistry of this tissue. Recent investigations have included the effects of
retinoid deficiency on the synthesis of
RNA and the identification of
RNA species associated with this
biological state, and also have included the effects of
retinoids on the synthesis of mucus-related
glycoproteins. Tracheal organ cultures from
retinoid-deficient hamsters have been used successfully to indicate the potency of synthetic
retinoids by monitoring the reversal of squamous
metaplasia. Techniques applied to this tissue have also served to elucidate features of the metabolism of
retinoic acid using high pressure liquid chromatography. In brief, formidable strides have been made in biochemistry specific to this important target tissue, despite the inability to acquire tracheobronchial epithelium in large quantities.