Studies of age-related changes in the metabolism of eosin in the rat

Male rats of different age groups maintained normally on laboratory chow were injected with eosin (2,4,5,7-tetrabromo-11-carboxyfluorescein) after which the biliary excretion of the dye was studied. In 3 age groups below 42 weeks, the dye was excreted as 2 compounds which were identified by thin-layer chromatography as unchanged eosin (Rf 0.90--0.91) contributing about 80--90% and one conjugated compound of Rf 0.43--0.47 (14--9%) which was shown to be a glucuronide. Eosin metabolites could not be traced in 30 and 42 week-old rats. This finding is discussed in relation to: (i) age and enzymic activity, and (ii) bio-activated metabolites of this dye which may induce biochemical or toxicological and carcinogenic lesions.