Phosphate Compounds in Vertebrate Red Blood Cells

This review brings together and discusses the significance of existing information about water-soluble (small molecule) organic phosphate constituents of red blood cells in different vertebrate species, with emphasis on 2,3 diphosphoglycerate (DPG), inositol pentaphosphate (IP<inf>5</inf>) ATP and guanosine triphosphate (GTP), compounds which may play an important role in respiratory physiology by modifying the affinity of hemoglobin for oxygen. Results on the distribution and concentration of these compounds in red cells of vertebrate animals can be summarized as follows 1) <it>DPG</it> High in mammals (except cats and ruminants) Absent in crocodilians squamata and fishes. High briefly in the bird embryo absent in adult. High briefly in turtle embryo low in juvenile low to absent in adult 2 <it>IP<inf>5</inf></it>. High in birds. Absent in mammals, crocodilians squamata and fishes (with the exception of <it>Arapaima gigas</it>). Low in turtles 3 <it>ATP</it> Intermediate in mammals. High in birds and turtles. Very high in squamata Intermediate to very high in fishes. Low in crocodilians 4) <it>GTP</it> Very low in mammals birds, reptiles and amphibians (except for small pool in <it>Rana</it> tadpole). Low to very high in fishes.