ABSTRACT
The present study was designed to see the effect of 13-cis retinoic acid [CRA] on albino rats skin tumour initiation by dimethylbenze [a] anthracene [DMBA] and promotion by 12-"o" tetra decanoyl-phorbol. 13 acetate [TPA]. Skin tumour was initiated by 20 [micro] g/2.0 ml DMBA twice a week in one group of rats. In an other group of rats tumour promoter TPA was applied in a dose of 2[micro]/0.2m1, after the application of initiator [DMBA] in the same dose twice a week. This study was continued for 20 weeks. In another groups of rats I 3-cis retinoic acid [CRC] was applied before the application of initiator [DMBA] and promoter [TPA]. Topical application of CRA resulted in 80% tumour inhibition when given before the DMBA and 70% when given before TPA. The results indicate that vitamin 'A" [CRA] inhibits both stages of tumour initiation and promotion