Evidence that the decreased liver folate status following vitamin B-12 inactivation in the mouse is due to increased loss rather than impaired uptake.

Using N2O to inactivated B-12, mouse liver polyglutamate distribution has been examined at short time intervals after injection of [3H]pteroyglutamate. An increased monoglutamate pool is found initially which is lost by 24 h. This finding strongly supports the suggestion that the reduction in total liver folate in vitamin B12 deficiency is due to increased loss rather than decreased uptake.