Formation of Ferrihæmoglobin of Isolated Human Hæmoglobin Types by Sodium Nitrite

Abstract

THE sensitivity of hæmoglobins to oxidation by potassium ferricyanide and sodium nitrite (NaNO₂) has been examined extensively^1,2. During treatment of oxyhæmoglobin with NaNO₂, both components are oxidized through a combination of different reactions, the total reaction being summarized as follows: NaNO₂ + 2R–Fe⁺⁺ O₂ + H₂O→NaNO₃ + 2R–Fe⁺⁺⁺OH + O₂ (ref. 2). The rate of ferrihæmoglobin formation by the action of NaNO₂ can be calculated from the sigmoid curve representing the relation between reaction time and per cent of ferrihæmoglobin and is expressed as the time required for 50 per cent oxidation of the hæmoglobin (T 1/2). It has been demonstrated that the hæmoglobin of cord red blood cells, which is composed mainly of fœtal hæmoglobin (Hb-F), is particularly sensitive to treatment with NaNO₂. Since the structural difference between Hb-F and Hb-A is located in one of the two types of polypeptide chains, Hb-F being composed of 2 α-chains and 2 γ-chains (α₂γ₂) and Hb-A of 2 α-chains and 2 β-chains (α₂β₂), the possibility is present that NaNO₂ will react differently with human hæmoglobin types of other structural composition.