Evidence for diazotization of 14C-sulfamethazine [4-amino-N-(4,6-dimethyl-2-pyrimidinyl)benzene[U-14C]sulfonamide] in swine. The effect of nitrite

Dietary nitrite greatly enhanced the conversion of orally administered 14C-sulfamethazine (4-amino-N-(4,6-dimethyl-2-pyrimidinyl)benzeneU-14C]sulfonamide; 14C-sulmet) to 14C-desaminosulfamethazine N-(4,6-dimethyl-2-pyrimidinyl)benzeneU-14C]sulfonamide; 14C-DA-sulmet] in swine. The disposition of 14C orally administered to swine as 14C-sulfamethazinediazonium tetrafluoroborate (4-N-(4,6-dimethyl-2-pyrimidinyl)sulfonamido] U-14C]diazonium tetrafluoroborate) was very similar to the disposition of 14C given to swine as 14C-sulmet in combination with nitrite. These results and other information discussed in the text provide evidence that 14C-sulmet, in the presence of nitrite under the acid conditions in the gastrointestinal tract, was diazotized and that this diazonium intermediate was converted to 14C-DA-sulmet and other unidentified 14C-labeled products.