The Influence Of Blood Gas Properties On Gas Tensions And Ph Of Ventral And Dorsal Aortic Blood In Free-SwimmingTuna, Euthynnus Affinis

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 varied from 34·5 to 91·7 mmHg, and ranged from 3·7 to 7 mmHg. 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 and to rise and pH to fall. Oxygen-combining curves for whole 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 Root effect. Although these in vitro properties of tuna whole blood are at variance with other published data on tuna they nevertheless substantiate our determinations made in vivo.