Absorption and excretion of 1-amino-2-naphthol-6-sulphonic acid in rats and rabbits.

1-amino-2-naphthol-6-sulphonic acid (ANSA) and compounds of similar structure are metabolites formed by azo reduction in mammals from several commonly used food colours, e.g. Sunset Yellow FCF and Food Red 17. At our institute it has been shown that ANSA produces bile duct proliferation when given orally to rabbits. Furthermore Orange RN which by azo reduction yields ANSA (and aniline) induce the same effect in pigs (Olsen et al., 1973) but not in rats (Gaunt et al., 1971). Using 35S-labelled ANSA the absorption and excretion as well as the localisation in the liver cell of ANSA was investigated in rats and rabbits. The results after p.o. administration shows that the rabbit absorbs and excretes into the urine a significant larger amount of ANSA (30-40%) than the rat (6-13%). The results after i.v. administration shows that some 60% of the injected dose is excreted in the urine in both species. In the rat 15-20% are recovered from the faeces, while only traces (0.1-0.5%) are found in faeces of rabbits. A significant amount of ANSA was retained in the blood and the liver of both species 24 and 48 hours after administration. After differential centrifugation of liver homogenates the majority of ANSA was found in the 9000 x g supernatant.