The Influence of Blood Gas Properties on Gas Tensions and pH of Ventral and Dorsal Aortic Blood in Free-Swimming Tuna, Euthynnus Affinis

Abstract

We have developed a technique for capture, anaesthetization, instrumentation and release of tuna and have made the first determinations of blood gas values in dorsal and ventral aortae of free-swimming tuna. Dorsal aortic Po2 varied from 34.5 to 91.7 mmHg, and Pcoco2 ranged from 3.7 to 7mmHg. Dorsal aortic blood [pHa = 7.77 ± 0.04 (8), mean ± one S.E.M. (N)] was more alkaline than ventral aortic blood [pHv = 7.65 ± 0.02 (7)]. Warming dorsal aortic blood from 25 to 35 °C in a closed system caused Po2 and PCOCO2 to rise and pH to fall. Oxygen-combining curves forwhole blood were sigmoid [mean Hill's number = 1.72 ± 0.05 (11), range 1.57-2.0]and P50 over the pH range found in free-swimming animals was 21 ± 1.75(8) mmHg. The CO2-induced Bohr coefficient (ΔlogP50/Δ pH) was −0.59 ± 0.046(30). Unusual features of CO2-combining curves are attributed to a significant Rooteffect. Although these in vitro properties of tuna whole blood are at variance withother published data on tuna they nevertheless substantiate our determinations madein vivo.