The influence of inorganic ions and pH on oxygenation properties of the blood in the gastropod mollusc Busycon canaliculatum

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Abstract
The oxygen affinity of Busycon canaliculatum blood decreases with increasing pH in the range 6.6–7.9, and increases from 7.9–8.5, which encompasses the physiological range under normoxic conditions. When inorganic ions are removed from the blood, the oxygen affinity of the hemocyanin increases, the reverse Bohr shift diminishes and the normal Bohr shift cannot be detected. The addition of physiological levels of NaCl restores much, but not all, of the oxygen affinity and the Bohr shifts remain reduced or absent. The addition of physiological levels of Ca+2 and Mg+2 to the NaCl solution restores virtually all of the oxygen equilibrium properties that characterize native blood.When the samples are buffered with CO2 instead of Tris Maleate, the salt and pH effects change above pH 7.9, which may be due to either an indirect effect of carbon anions on divalent cation activity or a heterotropic effect of CO2 on the hemocyanin molecule.The pH dependence of oxygen affinity changes at low temperature.