Blood oxygen equilibria and theoretical models. I. Effect of protons in trout (Salmo gairdneri) and human red cells, in absence of organic phosphates.
1. Oxygen equilibrium curves were measured on red cells that had been depleted of organic phosphates, for rainbow trout red cells between pH 7-9, at 15 and 20 degrees C, and for human red cells between pH 6.8-8.0, at 37 degrees C. 2. The data were fitted to the models of Adair and of Monod et al. (MWC model). Parameters were estimated by the non-linear least-squares method, from which the number of Bohr protons released during oxygenation was calculated. 3. For trout as for human red cells, the pH affects the first step of oxygenation and the overall oxygenation in nearly equal proportion. For human red cells, the association constant for binding of the last oxygen, expressed by k4 or kR, is not affected by pH, indicating that the R structure is free of constraints. For trout red cells, there is a pronounced pH dependence of this constant at low pH, which is about 10-fold increased between pH 7-9. This corresponds to the Root effect that impairs the T----R transition, and confirms previously published data for normal trout and human red cells. 4. For trout red cells, small functional heterogeneity is evidenced, despite Hb multiplicity, and effect seems linked to the level of temperature. 5. The specific effect of organic phosphates, evident for human red cells, contrasts with a lack of effect for trout red cells, when taking into account the intracellular pH values.
D000465:Algorithms; D000818:Animals; D004912:Erythrocytes / Q000032:analysis*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010100:Oxygen / Q000097:blood*; D010710:Phosphates / Q000097:blood*; D011522:Protons; D012016:Reference Values; D012487:Salmonidae / Q000097:blood*; D014337:Trout / Q000097:blood*
D010710:Phosphates; D011522:Protons; D010100:Oxygen