Serum "uracil+uridine" levels before and after vitamin B12 therapy in pernicious anaemia.

The serum "uracil+uridine" levels, expressed as uracil, have been measured in 10 cases of pernicious anaemia both before and after treatment, and compared with the levels in 97 normal subjects. The mean pre-treamtent value (8.82 mumol/1., range 6.0-12.0 mumol/1.) differed significantly from that of the normal controls (15.7 mumol/1., range 5.7-40.5 mumol/1., t = 8.8, P less than 0.001). This confirms the low serum uracil level previously reported in pernicious anaemia relapse. The level rose progressively after treatment, reaching a maximum on the fourth day (mean 17.85 mumol/1., range 9.3-23.4 mumol/1.). This was not significantly different from the mean of the normal control group. The difference between the pre- and post-treatment levels was significant on days 3,4 and 5 (P less than 0.005, P less than 0.001 and P less than 0.005 respectively) and the rise preceded the reticulocyte response by 24 h. A further case was treated with pysiological doses of vitamin B12 (2 mug daily for 6 d) and a similar rise in the serum uracil level noted. These results are not explained by any of the known functions of vitamin B12. They are, however, similar to the changes in the serum methionine levels previously reported in pernicious anaemia. The latter were readily explained by the known action of vitamin B12 on "de novo" methionine synthesis and it is suggested that the synthesis of uracil, like that of methionine, might be influenced by vitamin B12 in man.