Isoelectric focusing of rabbit transcobalamin from serum and cerebrospinal fluid

Isoelectric focusing in agarose gel separated rabbit transcobalamin into five to eight isopeptides with isoelectric point (pI) 5.4-6.8. Three different sets of patterns were observed in serum samples from 34 rabbits and in cerebrospinal fluid samples from 10 rabbits as a given pattern in serum corresponded to a given pattern in cerebrospinal fluid. Serum contained higher substance concentrations of acidic isopeptides than cerebrospinal fluid. No correlation was found between the isopeptide patterns and the unsaturated cobalamin-binding capacity. The unsaturated cobalamin-binding capacity of cerebrospinal fluid was high in relation to the protein concentration (0.5-1.3 nmol/l) compared to that of serum (6.6-22.8 nmol/l). The data suggest synthesis of transcobalamin into the cerebrospinal fluid.