Basal N-nitrosoproline formation and excretion in the ferret.

Quantitative balance studies indicated that ferrets (Mustela putorius furo) on purified diets excreted approximately four times more N-nitrosoproline than they ingested. This basal N-nitrosoproline excretion was not dependent on dietary nitrate intake, as high levels of dietary [15N]nitrate did not result in the incorporation of 15N into the excreted N-nitrosoproline. This indicates that there are at least two sources of endogenous N-nitrosoproline formation, one linked to dietary nitrate and one independent of dietary nitrate. The latter may result from an intermediate in the endogenous synthesis of nitrate.