COMPARATIVE-STUDY OF THE OXYHEMOGLOBIN DISSOCIATION CURVE OF 4 MAMMALS - MAN, DOG, HORSE AND CATTLE

1. The entire oxygen dissociation curve (ODC) and the effects of tempe rature, pH and 2,3-diphosphoglycerate (DPG) on this curve, have been c ompared in four mammalians: man, dog, horse and cattle. 2. If the oxyp horic capacities are similar between these species (around 1.39 ml O-2 /gHb), their P50, measured in standard conditions, i.e. at pH 7.4; pCO (2) 40 mmHg and T 37 degrees C, varies between 23.8 (+/-0.8) mmHg for the horse, 25.0 (+/-1.4) mmHg for cattle, 26.6 (+/-1.2) for man and 28 .8 (+/-2.6) mmHg for the dog. 3. The higher dispersion of the dog's P5 0 is due to difference between breeds; in seven breeds investigated, t he P50 ranges from 25.8 (spaniel) to 35.8 (hound). 4. We noted no sex difference in the four species. 5. The DPG level is confirmed to be lo w in cattle (<l mu mol/gHb) as compared to man (13.5 +/- 2.1 mu mol/gH b), horse (16.9 +/- 1.1 mu mol/gHb) and dog (19.4 +/- 2.8 mu mol/gHb). 6. The oxygen exchange fraction defined as the difference in vol% bet ween a pO(2) of 80 and 35 mmHg is, respectively, 3.6 (+/-0.6) vol% for cattle, 4.0 (+/-0.4) vol% for the horse, 5.5 (+/-0.5) vol% for man an d 6.6 (+/-1.7) vol% for the dog. 7. The position and shape of the ODC, as well as T, DPG and pH effects, indicate that the haemoglobin of ma n and dog seem better adapted to O-2 delivery as compared to the horse and cattle.