Chromatographic and Bioautographic Estimation of Plasma Cobalamins in Various Disturbances of Vitamin B12 Metabolism

Abstract

1. This paper reports a survey of values for individual plasma cobalamins in normal subjects, hospital controls, and patients with vitamin B₁₂ deficiency and diseases in which there are disturbances of B₁₂ metabolism. The values were obtained by thin-layer chromatography and bioautography followed by photometric scanning or visual assessment. 2. Normal plasma contains methylcobalamin (the predominant component), deoxyadenosylcobalamin and hydroxocobalamin. The latter two compounds are not separable in the solvent system routinely used. In some samples there were traces of cyanocobalamin. The ratio of methylcobalamin to deoxyadenosylcobalamin plus hydroxocobalamin, normally greater than 1·0, was reduced in B₁₂ deficiency. Many cases of untreated pernicious anaemia showed a high proportion (up to 40%) of cyanocobalamin. In folate deficiency there was no consistent change in individual cobalamins. Patients with leukaemias and liver disease showed a variety of changes, some attributable to alterations in plasma binding capacity and loss of deoxyadenosylcobalamin from the liver. 3. After oral or parenteral administration of cyanocobalamin, plasma cyanocobalamin increased and there was evidence of conversion to methylcobalamin. After parenteral administration of methylcobalamin, this compound increased in the plasma, but deoxyadenosylcobalamin plus hydroxocobalamin did not change. 4. Possible reasons for pathological changes in individual plasma cobalamins are discussed.