A preliminary investigation of promotion of brain tumours by hexachlorophane in Sprague-Dawley rats transplacentally exposed to N-ethylnitrosourea.

Two-stage carcinogenesis (initiation and promotion) has been demonstrated in various mammalian tissues, but there is no conclusive evidence that it occurs in the nervous system. The present work has investigated the possibility that it might occur in the brain of the rat. Pregnant Sprague-Dawley rats were given an initiating dose (10 mg/kg intravenously (i.v.)) of N-ethylnitrosourea (ENU), which resulted in a low but consistent yield of brain tumours in the offspring. The dose was determined in a prior dose-response investigation. The 'initiated' offspring were treated postnatally with the putative promoter, hexachlorophane, and its ability to increase tumour incidence was examined by standardized step sectioning of the brain from rats killed at 6 months. There was no evidence of promotion of ENU-induced brain neoplasms by hexachlorophane in the rat. The experimental procedure led to a reproducible incidence of glial tumours in the pups.