V- «*P- Biol. (i977). 67, 77-88 yy With 6 figures Printed in Great Britain pH AND HAEMOGLOBIN OXYGEN AFFINITY IN BLOOD FROM THE ANTARCTIC COD DISSOSTICHUS MAWSONI BY JESPER QVIST*. ROY E. WEBER, ARTHUR L. DEVRIES AND WARREN M. ZAPOL Department of Anesthesia, Gentofte Hospital, DK-2900 Hellerup, Denmark; Department of Zoophysiology, University of Aarhm, DK-8000 Aarhus, Denmark; Scripps Institute of Oceanography, La Jolla, California, U.SJi..; and Department of Anesthesia, Massachusetts General Hospital, Boston 02114, Massachusetts, U.S.A. {Received 10 September 1976) SUMMARY Blood pH in the antarctic cod (Dissostichus mawsom) and in two Trematomus species, occurring at —1-9 °C, is extremely high (~ 8-2 to 8-3). This supports and extends Rahn's (1966) model for the temperature—pH relationship in cold-blooded vertebrates. The blood of D. mawsoni shows a low oxygen affinity ( P w ~ 14*5 mmHg at pH 8-16 and —1-9 C C). Despite normal in vitro temperature and pH sensitivities, blood P M increases only slightly when live fish are temperature- stressed ( + 4-0 °C), or become acidotic as a result of agitational stress (blood pH 7*71), primarily as a result of compensatory decreases in blood ATP levels. Oxygen-binding properties of' stripped' (cofactor-free) solutions of D. maw- soni haemoglobin were measured in attempts to elucidate the molecular mechanisms involved in the function of the pigment. INTRODUCTION Fishes live in environments that vary greatly in physical and chemical properties. Their blood thus transports oxygen under very different conditions. Accordingly, the respiratory properties of the blood in fishes vary widely, both in intrinsic oxygen- binding characteristics of the haemoglobin and in the intracellular factors which influence its oxygenation properties. Oxygen transport in the blood of antarctic fishes is of considerable physiological interest. The physico-chemical conditions in antarctic waters are characterized by greater stability than the temperate regions. In McMurdo Sound, Antarctica, where the fishes used in this study originate, the water temperature is low (mean value, —1-9 °C) and shows only slight variation (—1-4 to — 2-0 °C) and the water remains virtually fully saturated with oxygen (Littlepage, 1965). • Present address: Jesper Qvist, M.D., Department of Anesthesia, Herlev Hospital, DK-2730 Herlev, Denmark. 6 E x B 67