SULFHYDRYL OXIDATION AND ACTIVATION OF RED-CELL K+-CL- COTRANSPORT IN THE TRANSGENIC SAD MOUSE

The SAD mouse is characterized by the expression of human SAD hemoglobin (Hb), a super S Hb with a higher tendency to polymerize than HbS due to the presence of two additional mutations, Antilles beta 23(Ile) and D Punjab beta 121(Glu). Monovalent cation transport was studied in erythrocytes from SAD-1 (Hb SAD = 19%) and beta-thal/SAD-1 (Hb SAD = 26%) mice. Erythrocytes containing Hb SAD exhibited dehydration, increased maximal rate of Na+-K+ pump, unchanged Rb+ flux via the Gardos channel, and increased K+-Cl- cotransport. K+-Cl- cotransport was defined as Cl--dependent (substitution with sulfamate or methanesulfonate) okadaic acid-sensitive K+ efflux. Volume regulatory decrease via K+-Cl- cotransport was also increased in swollen SAD erythrocytes compared with controls. K+-Cl- cotransport was stimulated by staurosporine in all mouse strains, but the extent of stimulation was reduced in beta-thal/SAD-1 mice. Treatment with dithiothreitol reduced K+-Cl- cotransport activity in SAD-1 and beta-thal/SAD-1 mice to levels similar to that of control strains, indicating that reversible sulfhydryl oxidation contributes to the activated state of K+-Cl- cotransport in mouse erythrocytes that express transgenic human Hb SAD.