Absorption and distribution of C.I. Solvent Red 24 in rats; intra-tracheal administration of 14C labeled dye.

1-((2-methyl-4-[(2-methyl phenyl)azo] phenyl)azo)-2-naphthalenol (C.I. Solvent Red 24) was prepared having a 14C label on the methyl group of the central ring and was administered in suspension intra-tracheally to a male and a female rat. After 96 hours in metabolism cages, the animals were sacrificed and 14C counted in various organs and in urine/feces samples taken periodically up to 96 hours. Absorbed colorant was defined as that percentage of the total dose of radioactivity not present in the lung parenchyma after 96 hours relative to the total amount recovered and amounted to about 60%. Of this, about 98% was excreted in the urine and feces, the latter being the major excretory pathway. No free colorant was found in either feces or urine. Fractional percentages of the absorbed radioactivity were found in various tissues including the liver, and 4-amino-2',3(14C) dimethylazobenzene was identified in the urine after acid hydrolysis.