Oxygen and carbon dioxide transport in the blood of the muskrat ( Ondatra zibethica)

We have investigated the oxygen and carbon dioxide transport properties of a small diving mammal, the muskrat ( Ondatra zibethica), where the hemoglobin primary structure has been established by Duffy et al. (1978). While whole blood oxygen capacity, the Haldane effect and the buffer capacity are not different compared to non-diving mammals of similar size, the Bohr effect and the oxygen affinity are increased. The oxygen half saturation pressure (P 50) was 26.1 mm Hg (3.5 kPa) at pH 7.4, and the Bohr effect −0.66 (related to plasma pH) and −1.07 related to cell pH. The high affinity of muskrat blood is caused by a comparatively small effect of 2,3 DPG and CO 2 on muskrat hemoglobin, that is accentuated through a relatively low concentration of 2,3-DPG in the muskrat red cell. The increased Bohr effect is caused primarily through the pronounced pH dependence of the oxygen-linked binding of 2,3-DPG. The weak interaction of muskrat hemoglobin with 2,3-DPG is not caused by substitutions at the binding site.