Effect of temperature on CO2 transport in elasmobranch blood

The effect of temperature on the CO 2 transport in the blood of some elasmobranchs ( Scyliorhinus, Mustelus, Torpedo ) was studied in the range of 9 to 25°C and at CO 2 tensions from 2 to 10 torr. The relative change in total CO 2 of whole blood was 2.5% per °C and that of the chemically bound CO 2 in true plasma4 % per °C. The log P CO 2 -pH lines shifted to a lower pH when the temperature was increased. The buffer capacity of true plasma was 10 meq/1 and per pH unit and that of separated plasma 4.2 meq/1 and per pH unit. These values were not affected by temperature. The buffer capacity of 1 g hemoglobin was 0.19 meq/1 pH unit. The molal heat of ionization was 7700 cal/mol. Human blood diluted to the same red cell volume displayed the same relationships between P CO 2 , C CO 2 and pH as dogfish blood. It is concluded that most of the CO 2 transport differences between man and dogfish are due to the lower concentration of the buffer proteins in dogfish rather than to different specific properties of the hemoglobin in dogfish and man.