Serum "uracil+uridine" levels in pernicious anaemia

The serum "uracil+uridine" level, expressed as uracil, has been 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 mumol/1). was significantly lower than in the controls (15.7 mumol/1., P less than 0.005). Nine of the former were complicated by stystemic illness but the clinical and haematological features in the remaining 12 were consistent with the diagnosis of pernicious anaemia in relapse. The serum uracil level in this group was even lower (10.21 mumol/1., P less than 0.01). This finding is unexpected in view of the generally accepted indirect role of vitamine 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 moreover 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.