Abstract
To the Editor: We were pleased to see the report by Donaldson et al.1 in the June 23 issue of the Journal showing that the response in transcobalamin II (TC II) to injected cyanocobalamin (CN Cbl) may be useful in the study of abnormal metabolism of TC II or Cbl (or both). We here complement their report by giving a variant of their basic technic, increasing the versatility of the procedure. In 10 control subjects we injected either of two amounts of standard pharmaceutical CN Cbl, 20 ng (saturation of plasma Cbl binding proteins) or 200 μg (supersaturation). It . . .