Ontogenetic changes in erythrocytic organic phosphates in the bullfrog, Rana catesbeiana

Abstract

AbstractThe metamorphosis of anuran tadpoles includes adjustments to different respiratory media and involves changes in all components of the respiratory system. Increased concentrations of erythrocytic organic phosphates decrease blood oxygen affinity in vertebrates. Nucleoside triphosphates (NTP), 2,3 diphosphoglycerate (DPG), inositol polyphosphate (I‐poly‐P) and total phosphate were measured in different stages of tadpoles, juveniles and adults. The concentrations of NTP, DPG, and I‐poly‐P were, respectively: 4.35, 1.90 and 1.12 μmol ml−1 RBC in tadpoles, and 1.80, 1.10 and 0.393 μmol ml−1 RBC in juveniles and adults. Molar ratios also decreased at metamorphosis: NTP/Hb from 1.83 to 0.49, DPG/Hb from 0.814 to 0.296, and I‐poly‐P/Hb from 0.483 to 0.061. The decrease in NTP occurs simultaneously with the transition from tadpole to adult hemoglobin type. The decrease in DPG parallels the decline in blood pH during metamorphosic climax. Levels of I‐poly‐P were not correlated with developmental changes of the respiratory system. The developmental stages of the decrease in red cell organic phosphate concentrations coincide with the suite of adaptive adjustments which lead to aerial respiration in metamorphosing bullfrogs.