Reticulocye Enrichment Of Zinc Protoporphyrin/Heme Discriminates Impaired Iron Supply During Early Development.

In infants and children, elevated whole blood zinc protoporphyrin/heme (ZnPP/H) measures iron-deficient erythropoiesis. Because immature erythrocytes are less dense than mature erythrocytes, we hypothesized that the sensitivity of ZnPP/H is improved if measured in the least dense cells. Blood was collected from control suckling, mildly and severely iron-deficient (ID) suckling rats. Cord blood was collected after uncomplicated pregnancies (control), diabetic pregnancies (severe ID) and after pregnancies at-risk for iron deficiency (mild ID). ZnPP/H was measured before and after a two-step density centrifugation to obtain the lightest 6.25% of erythrocyte (top fraction). The difference between whole blood and top fraction was defined as DeltaZnPP/H. In rats, although the whole or top ZnPP/H differed by postnatal age, DeltaZnPP/H was greatest after the interval with least body iron accrual. In either rats or humans with mild ID, whole blood ZnPP/H was similar to, but DeltaZnPP/H was greater than controls. In rats and newborn humans, DeltaZnPP/H is more sensitive than whole blood ZnPP/H in identifying conditions associated with impaired erythrocyte iron delivery and may become a useful tool in measuring erythrocyte iron incorporation in early development.

Blohowiak SE, Chen ME, Repyak KS, Baumann-Blackmore NL, Carlton DP, Georgieff MK, Crenshaw TD, Kling PJ.

Department of Pediatrics [S.E.B., M.E.C., K.S.R., N.L.B.-B., D.P.C., P.J.K.], Department of Animal Sciences [T.D.C.], University of Wisconsin, Madison, WI 53715; Department of Pediatrics [M.K.G.], University of Minnesota, Minneapolis, MN 55455.