Local treatment with 1-chloro-2,4-dinitrobenzene is a new therapy for alopecia areata [1 -3]. The application of this chemical leads to a contact dermatitis on the site of administration. It is assumed that the immunological reaction influences this disease by stimulating the hair roots to regrow. The clinical remission requires continuous application of DNCB. There are few reports concerning the toxicological effects of DNCB and nothing is known about possible mutagenic activity. For this reason, we examined the influence of local treatment with DNCB on the cytochrome P-450 system of the skin and liver of rats. In addition, we have investigated the mutagenicity of DNCB in the salmonella/microsome assay.
Adult female Wistar rats (approximately 260 g body weight, Zentralinstitut ftir Versuchstierzucht, Hannover) were treated with a 0.5 % acetone solution of 1chloro-2,4-dinitrobenzene (98 % pure, Merck-Schuchardt, Mtinchen, FRG). One milliliter of the solution was applied locally to the shaved back of the rats (2 x 2 cm) twice weekly over a period of 4weeks. Control animals were treated with aceto'ne only. In liver and skin the following parameters were determined: Cytochrome P-450 content, deethylation of 7-ethoxycoumarin, reduction of cytochrome c, hydroxylation of 3,4-benz(a)pyrene [4]. 9
Salmonella/microsome assay: DNCB was dissolved in acetone, doses ranged from 1 -100 lag per plate. Bacterial strains: Salmonella typhimurium TA 100 and TA 98 were used as indicator organisms. The Salmonella/microsome test was carried out according to Ames [5]. The experiments were performed with and without a mammalian metabolising system (S-9mix). The postmitochondrial supernatant (S-9) was obtained from 8 to 12-week-old'male rats (Wistar II).
A single i.p. injection of Aroclor-1254 (500mg/kg b.w.) was given to the animals 5 days before they were killed. Statistical evaluation was carried out by Wilcoxon rank test, mutagenicity was considered at P < 0.05 [6].
As to the clinical features, the rats showed distinct dermatitis at the sites of DNCB application, whereas no reaction could be detected in the controls.
The biochemical parameters of the treated animals did not differ significantly from the controls (Table 1). Mutagenic activity of DNCB could be demonstrated in