The respiratory properties of the blood of two diving rodents, the beaver and the water vole

Abstract

The HbO 2 dissociation curves were determined at CO 2 tensions of 40 and 105 or 140 mm Hg in blood from five beavers, Castor fiber, and five water voles, Arvicola terrestris. The O 2 tension giving 50 per cent oxygenation of the hemoglobin (T 50) was 23.3 and 38.4 mm Hg at pH 7.40, and the Bohr factor (Δlog T 50/ΔpH) was −0.56 and −0.54 in beavers and water voles respectively. The O 2 capacities were 16.1 and 19.4 vol % corresponding to 11.9 and 14.4 g/100 ml of Hb. Also, the CO 2 dissociation curves of reduced and oxygenated blood were constructed. The CO 2 content of oxygenated blood at pH 7.40 and 40 mm Hg of CO 2 was 46 and 43 vol % and the Haldane effect 5.4 and 4.8 vol % CO 2. The buffering capacity (ΔHCO 3 −/ΔpH) was −27 and −34 meq/l in the beaver and water vole respectively. The beavers were submitted to experimental diving and blood was sampled from a central artery and vein. In vivo HbO 2 sat. %, O 2 tension and pH values were used to construct the dissociation curves of pH 7.40. The respiratory properties of the blood in these species, which are habitual divers, do not reflect any significant adaptation to the hypoxia and hypercapnia associated with diving. The present and previously published results on other diving mammals are compared and discussed.