Metabolism and distribution of two 14C-benzidine-congener-based dyes in rats as determined by GC, HPLC, and radioassays.
The absorption, distribution and metabolism of the azo dyes Direct- Red-2 (992596) and Direct-Blue-15 (2429745) were studied. Male Fischer-344-rats were given single doses of 2 milligrams of dye. Urine was collected at intervals and assayed for metabolites radiochemically and by high peformance liquid chromatography. Peak excretion occurred after 8 hours with 6.6 percent of the Direct-Blue- 15 found in urine and 44 percent in the feces. Direct-Red-2 after 8 hours was 8.3 percent in the urine and 35 percent in feces. 3,3- dimethylbenzidine (119937) accumulated in tissue as follows: from Direct-Blue-15 (in microgram equivalents) kidney, 1.14; liver, 4.1; lung, 0.67; stomach, 0.588. From Direct-Red-2 microgram equivalents were 2.9, 8.6, 6.9, and 2.9 for kidney, liver, lung, and stomach, respectively. The authors conclude that both dyes significantly accumulate in the liver, a target organ for rats dosed with benzidine and the site of tumors in rats dosed with benzidine based azo dyes.