Oxygen dissociation curves of muscle haemoglobin

Abstract

The function of muscle haemoglobin in respect to its combination with oxygen has now been made clear. It has been shown independently by two observers, Theorell (1934) and the present writer (R. Hill, 1933), to have a higher affinity for oxygen than the haemoglobin of circulation. The muscle haemoglobin has the positions of maximum absorption in the visible region of the spectrum at 5815 A and 5446 A, while those of the haemoglobin of the blood are at about 5770 A and 5420 A. It can be easily shown that an extract of red muscle having its ∝ band at about 5790 A (that is, in a position intermediate between the ∝ bands of the two haemoglobins) gives on partial evacuation a shift of the ∝ band to the red. This shows qualitatively the higher affinity for oxygen of the muscle haemoglobin. A convenient method of determining the dissociation equilibrium with oxygen on small amounts of dilute haemoglobin was then devised and applied to the problem. Meanwhile, Theorell achieved the isolation of muscle haemoglobin from the heart of the horse in a crystalline state and determined its dissociation curve by the established method for strong solutions. The results of these investigations are in agreement. Theorell’s series of investigations on the muscle haemoglobin of the horse are as elegant as they are complete. The present paper describes experiments on the heart muscle haemoglobin of the ox, sheep, dog, and goose. The characteristic hyperbolic shape of the muscle haemoglobin dissociation curve being found in each case. The method of determining the dissociation curve is given in detail. A dilute oxyhaemoglobin solution saturated with atmospheric oxygen is added in successive amounts to haemoglobin of the same concentration contained in an evacuated vessel. The liquid is shaken to obtain gaseous equilibrium, and spectroscopic determinations are made after each addition. The total pigment concentration in the tube is not altered during the experiment. We then have the required data for a dissociation curve.