Effects of phenobarbital and carbazole on carcinogenesis of the lung, thyroid, kidney, and bladder of rats pretreated with N-bis(2-hydroxypropyl)nitrosamine.

Studies were made on potential modifying effects of phenobarbital (PB) and carbazole on tumor development induced by N-bis(2-hydroxypropyl)nitrosamine (DHPN), a wide-spectrum carcinogen in rats. Effects on the lung, thyroid, kidney, bladder and liver were investigated. Male F344 rats were given 0.2% DHPN in their drinking water for 1 week and then 0.05% PB or 0.6% carbazole in their diet for 50 weeks. Control animals were treated with either DHPN or PB or carbazole only. Neither PB nor carbazole affected the incidence or histology of lung tumors. However, PB promoted the development of thyroid tumors and preneoplastic lesions of the liver, while carbazole promoted the induction of renal pelvic tumors.