Anion transport in normal erythrocytes, sickle red cells, and ghosts in relation to hemoglobins and magnesium.
"Band 3," an integral membrane protein of red blood cells, plays a relevant role in anionic transport. The C- and N-terminal portions of band 3 are cytoplasmatics, and the last is the link site for different glycolitic enzymes, such as glyceraldehyde-3-phosphate dehydrogenase, aldolase, phosphofructokinase, and hemoglobin. All or some of these interactions on the CDB3 protein could allow a subtle modulation of anion flux. The interaction among HbA, Mg(2+), and membrane proteins has been sufficiently investigated, but not the effect of Mg(2+) on pathological hemoglobin in relation to the influx of the SO(4)(2-). The aim of this study was to evaluate the involvement of hemoglobin S in sulfate transport. This has been measured with native and increased concentrations of Mg(2+), using normal erythrocytes containing HbA, sickle red cells containing HbS, or ghosts obtained from both erythrocytes and normal erythrocytes ghosts with HbS added. The magnitude of the SO(4)(2-) rate constant measured in normal red blood cells increased markedly when measured in the presence of varied Mg(2+) concentrations. The results show that a low increase of intracellular Mg(2+) concentrations exercises a different HbA modulation on band 3 protein and consequently higher anion transport activity. The same experiments carried out in sickle red cells showed that the SO(4)(2-) rate constant measured in the presence of native concentrations of Mg(2+) was normal, compared to normal red cells, and was not affected by any increase of intracellular Mg(2+). Our suppositions with regard to the importance exercised by the hemoglobin and the Mg(2+) on the SO(4)(2-) influx were confirmed by comparison of the data obtained through measuring SO(4)(2-) influx with native and increased concentrations of Mg(2+) in both normal and sickle red cell ghosts. Both revealed the same sensitivity to Mg(2+) due to withdrawal of hemoglobins. The incorporation of HbS in normal as well as in sickle red cell ghosts reduced the Mg(2+) response to sulfate influx in both the reconstituted ghosts. Our research demonstrated that the different effects exercised on the rate constants of SO(4)(2-) influx in normal (HbA) and sickle red cells (HbS) by the increased intracellular Mg(2+) could be ascribed to the physical-chemical influence exercised either on the hemoglobins or on the intracellular contents of erythrocytes.
Teti
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Institute of General Pathology, Faculty of Medicine and Surgery, Torre Biologica IV Piano, Policlinico "G.Martino," Via Consolare Valeria, 98125, Messina, Italy.
Venza
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I
Crupi
M
M
Busà
M
M
Loddo
S
S
Romano
L
L
D000328:Adult; D000755:Anemia, Sickle Cell / Q000097:blood*; D000838:Anions / Q000378:metabolism; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D005260:Female; D006441:Hemoglobin A / Q000378:metabolism; D006451:Hemoglobin, Sickle / Q000378:metabolism*; D006801:Humans; D008274:Magnesium / Q000378:metabolism*; D008297:Male; D012016:Reference Values; D013431:Sulfates / Q000378:metabolism*
D000838:Anions; D006451:Hemoglobin, Sickle; D013431:Sulfates; D006441:Hemoglobin A; D008274:Magnesium