Relationship between the major phosphorylated metabolic intermediates and oxygen affinity of whole blood in the loggerhead (Caretta caretta) and the Green Sea Turtle (Chelonia mydas) during development.

(1) 2,3-Diphosphoglyceric acid (2,3-DPG) is present in the erythrocytes (RBC) of the 68-day loggerhead turtle embryo and 44-day green sea turtle embryo at levels of 7.4 and 5.5 μmoles/ml of RBC, representing the major organic phosphate during the latter period of embryonic development. (2) Inositol pentaphosphate (IPP) is absent in the red blood cells of the embryos of both the loggerhead and green sea turtle. (3) Near equimolar amounts of 2,3-DPG and IPP are present in the erythrocytes of the adult loggerhead and green sea turtle. The total concentration of these two organic phosphates is approximately 0.75 μmoles/ml of RBC in the adult of both species. (4) There is a switch from embryonic to adult hemoglobin during development of these two species of turtles; the two embryonic bands have identical electrophoretic mobilities, whereas the two adult bands migrate differently on cellulose acetate at pH 8.6. (5) The whole blood oxygen affinity of the adult loggerhead and green sea turtle is 60.3 and 32.6 Torr, respectively. (6) The stripped adult hemoglobins in these two species of turtles show no change in oxygen affinity upon addition of 2,3-DPG, ATP, or IPP. (7) It therefore appears unlikely that whole blood oxygen affinity is controlled by organic phosphate modulation of hemoglobin function in these species of turtles.