Plasma total transcobalamin I - Ethnic/racial patterns and comparison withlactoferrin

Plasma total transcobalamin (TC) I levels were measured in 434 healthy volu nteers by radioimmunoassay (RIA). The results were analyzed for demographic patterns and were compared with lactoferrin, cobalamin, homocysteine, and chemistry panel results. Plasma TC I was higher in blacks than in other ethnic/racial groups and hig her in women than in men. TC I levels did not correlate with lactoferrin le vels. Lactoferrin showed significant ethnic differences also, but, unlike T C I, its levels were highest in whites. TC I levels correlated with cobalam in but not homocysteine levels. Neither TC I nor lactoferrin correlated wit h chemistry panel results, including creatinine, total protein, albumin, la ctate dehydrogenase, and alkaline phosphatase levels. The demonstration with an RIA that directly measures total TC I that plasma levels are significantly higher in blacks than in other groups may explain the well-known higher cobalamin levels in blacks. Surprisingly, plasma lac toferrin, which has the same cellular sources as TC I, does not correlate w ith plasma TC I levels and shows dissimilar demographic patterns; lactoferr in levels are highest in whites. These findings suggest that regulation and /or secretion of these 2 proteins differ even though their localization and expression patterns in myeloid precursors are similar.