Evidence of a protective role of the Grados channel against hemolysis in murine spherocytosis

It has been shown that mice with complete deficiency of all 4.1R protein isoforms (4.1/) exhibit moderate hemolytic anemia, with abnormal erythrocyte morphology (spherocytosis) and decreased membrane stability. Here, we characterized the Gardos channel function in vitro and in vivo in erythrocytes of 4.1/ mice. Compared with wild-type, the Gardos channel of 4.1/ erythrocytes showed an increase in Vmax (9.75 1.06 vs 6.08 0.09 mM cell minute; P < .04) and a decrease in Km (1.01 0.06 vs 1.47 1.02 M; P < .03), indicating an increased sensitivity to activation by intracellular calcium. In vivo function of the Gardos channel was assessed by the oral administration of clotrimazole, a well-characterized Gardos channel blocker. Clotrimazole treatment resulted in worsening of anemia and hemolysis, with decreased red cell survival and increased numbers of circulating hyperchromic spherocytes and microspherocytes. Clotrimazole induced similar changes in 4.2/ and band 3/ mice, indicating that these effects of the Gardos channel are shared in different models of murine spherocytosis. Thus, potassium and water loss through the Gardos channel may play an important protective role in compensating for the reduced surface-membrane area of hereditary spherocytosis (HS) erythrocytes and reducing hemolysis in erythrocytes with cytoskeletal impairments