Marco B. Rust, Seth L. Alper, York Rudhard, Boris E. Shmukler, Rubén Vicente, Carlo Brugnara, Marie Trudel, Thomas J. Jentsch, Christian A. Hübner
J Clin Invest.
2007;
117(6):1708–1717
doi:10.1172/JCI30630
This article Copyright © 2007, The American Society for Clinical Investigation
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K
-Cl cotransport activity in rbc is a major determinant of rbc volume and density. Pathologic activation of erythroid K-Cl cotransport activity in sickle cell disease contributes to rbc dehydration and cell sickling. To address the roles of individual K-Cl cotransporter isoforms in rbc volume homeostasis, we disrupted the Kcc1 and Kcc3 genes in mice. As rbc K-Cl cotransport activity was undiminished in Kcc1–/– mice, decreased in Kcc3–/– mice, and almost completely abolished in mice lacking both isoforms, we conclude that K-Cl cotransport activity of mouse rbc is mediated largely by KCC3. Whereas rbc of either Kcc1–/– or Kcc3–/– mice were of normal density, rbc of Kcc1–/–Kcc3–/– mice exhibited defective volume regulation, including increased mean corpuscular volume, decreased density, and increased susceptibility to osmotic lysis. K-Cl cotransport activity was increased in rbc of SAD mice, which are transgenic for a hypersickling human hemoglobin S variant. Kcc1–/–Kcc3–/– SAD rbc lacked nearly all K-Cl cotransport activity and exhibited normalized values of mean corpuscular volume, corpuscular hemoglobin concentration mean, and K+ content. Although disruption of K-Cl cotransport rescued the dehydration phenotype of most SAD rbc, the proportion of the densest red blood cell population remained unaffected.