Distribution and metabolism of aflatoxin B1 in the marmoset monkey (Callithrix jacchus)

Whole-body autoradiography of [³H]aflatoxin B₁ (³H-AFB₁) inmarmoset monkeys (Callithrix jacchus) showed a localizationof bound labelling, in addition to the liver, in the nasal olfactoryand respiratory mucosa and the mucosa of the nasopharyngealduct, the pharynx, the larynx, the trachea and the oesophagus.In vitro microautoradiography of these tissues incubated with³H-AFB₁ showed a localization of bound radioactivity in somecells in the epithelial linings of the tissues. This bindingwas abolished when the incubations were performed in the presenceof the cytochrome P-450 inhibitor metyrapone. These resultsindicate a cytochrome P-450-dependent bioactivation of AFB₁in some structures in the epithelia of the nasal olfactory mucosaand the upper respiratory and alimentary pathways, in additionto the liver, in the marmoset monkey. Quantitation of the invitro formation of tissue-bound radioactivity from the ³H-AFB₁showed that the nasal olfactory mucosa had the highest capacityto form bound metabolites among the tissues examined. Liquidchromatography of lipid-soluble metabolites formed by the nasalolfactory mucosa and the liver showed that aflatoxin M₁ (ATM₁)was the major metabolite. AFM₁ was also the major metabolitefound in the liver in vivo. In the pigmented tissues of themarmosets there was an accumulation of nonmetabolized AFB₁.This can be related to a melanin-affinity of AFB₁. The describedtissues with a capacity to accumulate and metabolize AFB₁ maybe potential targets for the carcinogenicity of this substancein the marmoset monkey.