Mini MCAT passage: Hair dye chemicals and cancer

An arylamine is an amine in which one or more of the hydrogen atoms are replaced by aromatic groups. Arylamines are common reagents used in the industrial production of hair dyes. Specific arylamines, such as 2-naphthylamine (Figure 1), pose a significant risk to hair stylists as the incidence of cancer from occupational exposure can range from 10 to 50%.

One physician is interested in studying the mechanistic pathway by which 2-naphthylamine causes cancer. She notes that conjugating processes in the liver convert 2-naphthylamine into a positively-charged metabolite that goes on to react within the body, especially with surfaces lined with transitional epithelium. To track the metabolism of 2-naphthylamine, a fluorescent dye known to bind 2-naphthylamine metabolites can be administered intravenously and detected in the urine. The dye is preferentially secreted by the nephron in the distal convoluted tubule and excreted in urine where it can be measured using a fluorescence assay.

Figure 1: 2-naphthylamine