Respiratory properties of blood of the gray seal,Halichoerus grypus

Abstract

1. This study examined the O2 and CO2 transport and acid-base properties of blood of the gray seal. Phocid seals use theblood as an oxygen store for aerobic metabolism during diving. Particular objectives were to determine whether CO2 exerts a specific effect on blood oxygen affinity, and whether the Bohr coefficient varies between different levels of oxygen saturation. 2. Hematocrit (0.50), blood hemoglobin concentration (12.8 mM heme) and cell hemoglobin concentration (25.4 mM) were, high compared to terrestrial mammals but similar to other seals (Table 2). Isoelectric focusing resolved the same four hemoglobin components in six individuals, with the most important components constituting 60% and 20% of the total. Oxygen affinity (P50=27.1 Torr at pH 7.4, 37.5°C) and equilibrium curve shape (nH=2.59) were similar to other phocid seals and terrestrial mammals (Tables 1,4). The Bohr coefficient for CO2 induced pH change (−0.51) was only slightly higher than that for fixed acid incuded pH change (−0.47), implying little oxygen-linked carbamino formation (Table 1). The bohr coefficients were at the upper end of the range found in terrestrial mammals, and did not vary with oxygen saturation (Table 1). 3. Blood buffer value was high (31.5 mM/pH), in accord with the high hemoglobin concentration (Table 3). The Haldane effect (−0.32 mol CO2 per mol O2, Fig. 2) was similar to those in blood of other seals and dog, but higher than that in human blood. Hydrogen ion uptake by hemoglobin upon deoxygenation (0.40 mol/mol O2) was greater than in human blood, in proportion to the larger fixed acid Bohr coefficient in the seal. 4. Blood of the gray seal, like that of other phocid seals, is distinguished from that of terrestrial mammals primarily by high hemoglobin concentration and oxygen capacity, which increase blood oxygen stores available for use during diving. Other properties are similar to those of terrestrial mammals or differ only as a consequence of the high hemoglobin concentration.