Alterations of specific pathways in HbS cells. Metabolites in red are increased in HbS cells versus normal RBCs. Metabolites in blue are decreased in HbS cells versus normal RBCs. Metabolites in black are unchanged in HbS cells versus normal RBCs. †Metabolites are related to RBC age and not SCD. *Metabolites are not detected in our study. **Metabolites cannot be set apart from its isomers. The solid black arrow indicates an enzymatic transformation; the solid blue arrow, a facilitated diffusion (passive transport) through RBC membrane; and the dashed blue arrow, a secondary active transport through the RBC membrane. (A) GSH metabolism, ascorbate metabolism, glycolytic activity, and pentose phosphate pathway. (B) Amino acid transport by RBC membrane and role of carnitine in cell membrane turnover. (C) Arginine and polyamine metabolism.