The occurrence of folate-derived pteridines in rat liver.

1. It has previously been shown that folate polyglutamates in the rat are catabolized almost exclusively via cleavage of the C-9--N-10 bond, resulting in the formation of pteridines and p-aminobenzoylglutamate. The latter catabolite is rapidly excreted, appearing in the urine as acetamidobenzoylglutamate and is undetectable in rat liver. 2. The pteridines catabolites on the other hand are retained to a much greater extent by the liver, forming an ever-increasing proportion of the retained radioactive tracer. 3. A possible role for these pteridines as cofactors in brain metabolism is discussed.