High affinity of lead for fetal haemoglobin

Abstract

In-vitro experiments using 203Pb were performed to identify lead-binding components in human haemoglobin. Sephadex A-50 ion-exchange chromatography of haemolysate showed that different types of haemoglobin had different affinities for lead. For the haemolysate from adults, lead was present in both Hb A (α2β2) and Hb A2 (α2δ2), whereas, in the haemolysate from new-born infants, the haemoglobin of fetal origin, Hb F (α2γ2) showed a much greater affinity for 203Pb than the adult haemoglobin Hb A (α2β2), obtained from maternal blood. Analysis of the 203Pb-labelled haemoglobin suggested that about 82% of 203Pb was in the globin polypeptide. Further analysis with carboxymethyl (CM) cellulose chromatography indicated that the γ globin of fetal origin had a higher affinity for 203Pb than the β globin, whereas α globin appeared to be unimportant in lead binding. The results of the different affinities for lead of different Hb types are discussed with regard to the effect of lead upon haemoglobin synthesis.