EXCRETION OF 4(5)-AMINO-5(4)-IMIDAZOLECARBOXAMIDE AND FORMIMINO-L-GLUTAMIC ACID IN FOLIC ACID AND VITAMIN B12DEFICIENT RATS

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Abstract
The excretion of 4(5)-amino-5(4)-imidazolecarboxamide (AIC) in the urines of normal rats, rats raised on a folic acid deficient diet, and rats raised on a vitamin B12deficient diet was measured. The AIC excretion was elevated 3-fold above normal in the B12deficient group and 1.5-fold above normal in the folic acid deficient group.No evidence could be found that the raised AIC excretion was associated with a block in the conversion of AIC to purines. The recovery of radioactive AIC in the urine after an intraperitoneal dose of 2 μmoles AIC per kg was not increased over normal in any of the deficient groups, and was significantly less than normal in the B12-deficient group. Most of the urinary radioactivity in all groups was in allantoin, uric acid, and purines.When a load of 220 μmoles of AIC per kg was administered there was no difference between the vitamin B12deficient and the normal groups in AIC recovery in the urine. When a load of 220 μmoles of urocanic acid per kg was administered, however, the B12-deficient group had an 18-fold increase over normal in Figlu excretion, and the folic acid deficient group a 17-fold increase. Thus, a substantial block in formimino-L-glutamic acid (Figlu) metabolism, but not in AIC metabolism, existed in the vitamin-deficient groups.Feeding a B12-deficient group a 2% methionine supplement reduced the Figlu excretion after a urocanic acid load to less than half that observed in B12-deficient groups without methionine supplementation, but had no influence on the AIC excretion.

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