Factors that “decrease” affinity of Hb for O2 promote greater unloading of O2 in the tissues
Increased Pco2
Increased acidity (Bohr effect)
Acidity also lowers maximal O2-binding capacity (Root effect)
Increased temperature
Organic phosphates
2,3-diphosphoglycerate (DPG) in most mammals
Inositol pentaphosphate (IPP) in birds
Nucleoside triphosphates in fishes