Urinary excretion of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in white, African-American, and Asian-American men in Los Angeles County

Meats, such as beef, pork, poultry, and fish, cooked at high temperatures p roduce heterocyclic aromatic amines, which have been implicated indirectly as etiological agents involved in colorectal and other cancers in humans, T his study examined the urinary excretion of a mutagenic/carcinogenic hetero cyclic aromatic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhI P), among 45 African-American, 42 Asian-American (Chinese or Japanese), and 42 non-Hispanic white male residents of Los Angeles who consumed an unrest ricted diet, Total PhIP (free and conjugated) was isolated from overnight u rine collections, purified by immunoaffinity chromatography, and then quant ified by high-pressure liquid chromatography combined with electrospray ion ization mass spectrometry, Geometric mean levels of PhIP in Asian-Americans and African-Americans were approximately 2.8-fold higher than in whites. T he urinary excretion levels of PhIP were not associated with intake frequen cies of any cooked meat based on a self-administered dietary questionnaire, in contrast to our earlier finding (Ji et al,, Cancer Epidemiol, Biomark, Prev., 3: 407-411, 1994) of a positive and statistically significant associ ation between bacon intake and the urinary level of 2-amino-3,8-dimethylimi dazo[4,5-f]quinoxaline (MeIQx) among this same group of study subjects, Alt hough there is a statistically significant association between urinary leve ls of PhIP and MeIQx (2-sided P = 0.001), 10 subjects (8%) displayed extrem e discordance between urinary PhIP and MeIQx levels. Several factors, inclu ding variable contents of heterocyclic aromatic amines in food, enzymic and interindividual metabolic differences, and analytical methodology determin e the degree of concordance between the urinary excretion levels of PhIP an d MeIQx, Accordingly, urinary excretion levels of a single heterocyclic aro matic amine can only serve as an approximate measure of another in estimati ng exposure to these compounds in humans consuming unrestricted diets.