During the development of these HbS reactive compounds, any effects on RBC permeability have received rather less attention. There are indications, however, that this might be significant. Thus, Lphenylalanine benzyl ester,whichwas found to reduce sickling, appears to partition into the RBC membrane and non-specifically inhibits transport systems including the Na+/K+ pump, the cation cotransporters (probably the Na+–K+–2Cl− cotransporter, NKCC) and the anion exchanger
(AE1) whilst also increasing passive cation leaks. No information is available on the aromatic aldehydes.