Erythrocyte Organic Phosphates and Hemoglobin Function in Birds, Reptiles, and Fishes

Abstract

Studies on the role of red blood cell organic phosphates in regulating oxygen transport and hemoglobin function in various species have emanated from several laboratories in the past few years. These data reveal that the organic phosphate composition of erythrocytes is certainly more diverse between classes of animals than previously recognized, that the kind and concentration of red cell organic phosphate modulator changes during development of the species and that the role of organic phosphates in modulating hemoglobin function is variable. For example in birds we believe that the changes in amounts and distribution of the intraerythrocytic organic phosphates account for the sudden changes in whole blood oxygen affinity during development of the embryo and young bird as well as in the mature bird. In the loggerhead and green sea turtle it appears that organic phosphate modulators regulate whole blood oxygen affinity during embryonic development but it is unlikely that whole blood oxygen affinity is controlled by organic phosphate modulation of hemoglobin function in the adult turtle. From the data now available on air-breathing fishes, it appears reasonable to consider that whole blood oxygen affinity may be regulated by a combination of organic phosphates that is the relative concentrations of the primary regulator (inositol-P₂ 2,3-DPG, or inositol P₅) may be rather stable whereas the nucleotide triphosphate (ATP and GTP) concentrations may fluctuate depending upon physiological demands upon the animal for oxygen.