Studies on avian erythrocyte metabolism: IX. Relationship of changing organic phosphate composition to whole blood oxygen affinity during development of the ostrich ( Struthio camelus camelus)

Abstract

(1) 2,3-Diphosphoglyceric acid (2,3-DPG) is present in erythrocytes (RBC) of the 37-day ostrich embryo at a concentration of 3.7 μmole/ml RBC, representing 23.5% of the cell phosphate. (2) Inositol tetraphosphate (inositol-P 4) is absent in red cells of the 37-day embryo, appears in the RBC about 63 days after hatch, and thereafter gradually accumulates to a level of 2.8 μmole/ml RBC in the adult bird, representing 30–35% of the cell phosphate. (3) Inositol pentaphosphate (inositol-P 5) is present in the erythrocytes of the 37-day embryo at a concentration of 0.8 μmole/ml RBC, reaches a peak level of 2.9 μmole/ml RBC by Day 63 after hatch, and thereafter declines to a level of 1.1 μmole/ml RBC in the adult bird. (4) The crossover time where the molar concentrations of inositol-P 5 and inositol-P 4 are equal in the erythrocyte appears to be about 150 days after hatch. (5) The p 50 of whole blood from the 37-day ostrich embryo, 5-day ostrich chick, and adult ostrich was 15.4, 31.8, and 24.9 Torr. The p 50 of whole blood immediately after hatch correlates best with an abrupt rise in ATP concentration but after 54 days posthatch correlates best with the appearance of increasing concentrations of inositol-P 4 and the decrease in concentrations of ATP and inositol-P 5. (6) The appearance of inositol-P 4 in the cells could be an adaptive mechanism for regulating oxygen supply by switching to a modulator which maintains a higher oxygen affinity than would a predominance of inositol-P 5.