Incubation of sickle cells with cystamine, a thiol reagent, resulted in the formation of an intracellular Sethylamine derivative. The rate of the reaction was dependent upon the cystamine concentration, the temperature, and the duration of the incubation. The cystamine-treated cells demonstrated a marked inhibition of sickling under hypoxic conditions, a decrease in their mean corpuscular hemoglobin concentration, and a significant increase in their oxygen affinity. The oxygen affinity of these cells was less dependent on their mean corpuscular hemoglobin concentration than that of untreated sickle cells. The minimum gelling concentration of Sethylamine deoxyhemoglobin S was slightly increased. Cystamine did not affect the intracellular pH nor the 2,3-di hosphoglycerate level. The exact contribution of the interrelated factors in cystamine inhibition of sickling (changes in oxygen affinity, mean corpuscular hemoglobin concentration, and minimum gelling concentration) has yet to be determined. Under hypoxic conditions, hemoglobin S (Hb S) molecules polymerize either in concentrated solutions (1, 2) or within erythrocytes (3, 4), giving rise to sickled cells. The polymerization of Hb S within the erythrocytes results in an abnormally low oxygen affinity (5, 6), which is dependent on Hb concentration within the cells containing Hb S (S cells) (7).Several agents have been reported to inhibit sickling, such as cyanate (8), nitrogen mustard (9), alkylurea (10), dimethyl adipimidate (11), and, more recently, bis(N-maleimidomethyl) ether (12). Cystamine, a thiol reagent (NH2-CH2-CH2-S-S-CH2-CH2-NH2), has been shown to bind to Hb (13). The Sethylamine Hb derivative migrated as a single electrophoretic band distinct from that of the unreacted Hb. This property provided a simple means of quantitation of the cystaminereacted fraction. The S-ethylamine Hb exhibited a high oxygen affinity and a reduced Bohr effect (14). In view of these properties, it was reasonable to suspect that cystamine could exert an antisickling effect.In the present report, the effects of cystamine on the sickling of S cells and on some related phenomena are presented.MATERIALS Fresh blood samples from individuals homozygous (SS), heterozygous (AS), and doubly heterozygous (SC) for sickle hemoglobinopathy and from normal adults were drawn into EDTA as anticoagulant. The composition of this anticoagulant was 1% EDTA, 0.6% NaCI, and 6% glucose (wt/vol); it maintained a constant level of 2,3-diphosphoglycerate (P2-G) in the erythrocytes during a minimum period of 7 days at 4°. Cystamine dichloride (2,2-dithio-bisethylamine dichloride) was provided was determined on packed frozen and thawed cells, at 370, with a Radiometer pH meter fitted with a microelectrode unit (type E 5021a). Erythrocyte P2-G level was determined according to Rose and Leibowitz (15). Hemolysates were prepared according to Drabkin (16). Hb electrophoresis was performed on cellulose acetate strips at pH 8.6 with Tris-EDTA-borate buffer (17); the proportions of the various frac...

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We have previously described the structural identification of the sickle hemoglobin variant Hb C Ziguinchor (alpha2A beta2 6 Glu replaced by Val, 58 Pro replaced by Arg). This hemoglobin was found in two generations (three members) of an African family. In two family members, the clinical picture resembled that typical of a sickle cell trait, while the third member showed a more extreme clinical condition due to complication by an iron deficiency anemia. The functional properties of Hb C Zig. in red blood cells or in dilute solutions were identical to those of Hb S. The gelling behaviour of deoxy Hb C Zig. was also indistinguishable from that of Hb S. These findings suggest that, in contrast to the case of Hb C Harlem, the second substitution in position beta58 in Hb C Zig. does not interfere with the intermolecular interactions determined by the sickle substitution.