INCREASED CATION PERMEABILITY IN MUTANT MOUSE RED-BLOOD-CELLS WITH DEFECTIVE MEMBRANE SKELETONS

Cellular cation homeostasis in mouse erythrocytes with defective membr ane skeletons was examined in three mouse mutants, hemolytic anemia (s ph(ha)/sph(ha)), spherocytosis (sph/sph), and normoblastosis (nb/nb), and compared with reticulocytes produced by repetitive bleeding of con genic normal mice. To assess reticulocyte maturity, nucleic acid and t ransferrin receptor contents were measured by fluorescence flow cytome try; mutant cells were somewhat more mature than normal reticulocytes by these criteria. Red blood cell (RBC) sodium contents (Na-c(+)) in h omozygous sph(ha)/sph(ha), sph/sph, and nb/nb animals were 30.1 +/- 0. 9, 28.9 +/- 0.3, and 26.9 +/- 1.5 mmol/L cell, respectively, whereas c ellular potassium (K-c(+)) was 102 +/- 2.6, 101 +/- 7.8, and 97.4 +/- 3.0. Na-c(+) and K-c(+) in normal reticulocyte preparations were 11.3 +/- 0.7 and 123 +/- 10, respectively. Net Na+ and K+ fluxes in the pre sence of ouabain were markedly increased in mutant RBCs. Sodium uptake was 14.8 +/- 1.6, 15.4 +/- 3.3, and 14.7 +/- 3.1 mmol/L cell/h in sph (ha)/sph(ha), sph/sph, and nb/nb mutants, respectively, whereas K+ los s was 17.0 +/- 4.0, 15.0 +/- 3.8, and 14.1 +/- 2.6. Normal mouse retic ulocytes gained Na+ at a rate of 3.9 +/- 1.0 mmol/L cell/h and lost K at 6.0 +/- 2.1, rates indistinguishable from those in mature mouse RB Cs. Potassium loss from sph(ha)/sph(ha) and nb/nb cells was not depend ent on the presence of a Na+ gradient, and net cation movements were i nsensitive to bumetanide (sph(ha)/sph(ha) and nb/nb RBCs) and to chlor ide replacement with sulfamate (nb/nb cells). We conclude that mutant mouse RBCs with dysfunctional membrane skeletons have increased passiv e permeability to monovalent cations. These findings support a role of the membrane skeleton in the maintenance of the membrane permeability barrier and suggest that the abnormal permeability associated with hu man hereditary spherocytosis and elliptocytosis may be a consequence o f the membrane skeleton defects reported in these disorders. (C) 1995 by The American Society of Hematology.