Does anyone know if the erythrocytes in venous blood have all uniformly % deoxygenated hemoglobin or some are fully oxygenated and others fully deoxygenated?
Maybe tomorrow I can find the reference, but in a recent conversation with Professor David Jameson it came up (if I recall correctly) that at most one subunit of the four in hemoglobin is deoxygenated in venous blood. Check his work on hemoglobin (David Jameson) and Gregorio Weber's.
Dear Kamellia,
You asked a very interesting question, a direct answer that I do not know about. Nevertheless, I hope that this article will be useful to you.
Article Single-cell measurement of red blood cell oxygen affinity
If we look at the oxygen dissociation curve under "normal" conditions shows that while arterial blood is 100% oxygenated, the average venous blood loses only about 40% Oxygen (deoxygenated) and still nearly 60% is oxygenated. Logically, all the red cells more or less should be having same proportions of these two forms of Hb. I do not have any reference for this. Just have a look at the graph for a ready reference. If there are differences in the regional circulations, I am not aware of it.
In the interior of red blood cells, the oxygen carrying proteins known as hemoglobin is in equilibrium with oxygen with relatively high reaction rates (37 s-1) whereas the oxygen release of hemoglobin from red blood cells is relatively lower ( 2 s-1) furthermore the diffusivity of oxygen in red blood cell rich regions is relatively low 3.32E-7 m2/s2. This means oxygen is transported relatively easily between red blood cells. (Consider this, if oxygen was unable to transfer between red blood cells, how would red blood cells be able to deliver oxygen to the tissue.) This implies that most red blood cells within a vessel contain similar distributions of oxygen.
To extend on Ramesh's answer, it is also important to note that the oxygen saturation curve for Hemoglobin is not constant in the body. Various factors including the increasing partial pressure of carbon dioxide, decreasing pH and increasing temperature all decrease hemoglobin's oxygen affinity (ie: right shift the oxygen equilibrium curve). Furthermore, 2,3-biphosphoglycerate can bind to deoxyhemoglobin further right shifting the oxygen equilibrium curve. From Article Relating oxygen partial pressure, saturation and content: Th...
we can see that changing one of these factors may alter the concentration of saturated hemoglobin by up to 10%. Compounding this further are potential stress conditions including anemia or exercise.Taking all of this together we might surmise that there may exist some conditions where venous blood meets that the oxygen saturation of red blood cells differs slightly. (ie a species of 65% saturated RBCs and 70% satruted RBCs) However, a new oxygen equilibrium will likely be formed very quickly.