Exposure level monitor of 3‐amino‐1,4‐dimethyl‐5H‐pyrido[4, 3‐b]indole, a dietary carcinogen, in rabbits

The present investigation describes a method for the detection of minute amounts of 3‐amino‐1, 4‐dimethyl‐5H‐pyrido[4, 3‐b]indole (Trp‐P‐1), a carcinogenic tryptophan pyrolysate, bound to the hemoglobin of erythrocytes and plasma from rabbits dosed orally with the dietary carcinogen. The method consists of the acid‐induced release of the dietary carcinogen adducts as the free carcinogen and their extraction with methylene chloride and subsequent quantitation by high‐performance liquid chromatography (HPLC). With this method, Trp‐P‐1 levels in plasma, platelets, and red blood cells were monitored for 12 weeks to determine a suitable indicator for estimating the exposure levels of the dietary carcinogen. The results suggest that Trp‐P‐1 in red blood cells that bound covalently to the hemoglobin is the most suitable for monitoring the long‐term exposure levels.