Serum ‘Uracil+Uridine’Levels in Pernicious Anaemia

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Abstract
The serum uracil + uridine level, expressed as uracil, was measured in 21 cases of vitamin B12 deficiency, in which the serum folate was normal, and compared with the level in 97 normal subjects. The level in the vitamin B12 deficient group (11.9 .mu.mol/l) was significantly lower than in the controls (15.7 .mu.mol/l, P < 0.005). Of the former, 9 were complicated by systemic illness but the clinical and hematological features in the remaining 12 were consistent with the diagnosis of pernicious anemia in relapse. The serum uracil level in this group was even lower (10.21 .mu.mol/l, P < 0.01). This finding is unexpected in view of the generally accepted indirect role of vitamin B12 in the methylation of deoxyuridine monophosphate to deoxythymidine monophosphate. Reasons are given for not accepting these results as reflecting the main biochemical lesion in vitamin B12 deficiency. Although they do not give direct support to an impairment in the methylation of deoxyuridine monophosphate, they do not exclude it as they test only one possible metabolic pathway, and they could represent the result of more than one action of vitamin B12 on uracil metabolism. They do show, however, that some aspect of uracil metabolism other than methylation is affected in vitamin B12 deficiency in man.