The Albumin/Globulin Ratio: A Technical Study.

In 1885-6 Kauder observed that globulin was precipitated from serum when the concentration of ammonium sulphate reached 24 to 29 per cent of full saturation and that its precipitation was complete when the concentration reached 36 to 46 per cent of complete saturation. Thereafter no further precipitation took place until the concentration reached 64 per cent of full saturation, when albu-min started to precipitate, its precipitation being complete at 90 per cent saturation. The simple qualitative differentiation of albumin from the globulin by their behaviour in the presence of ammonium sulphate is based on this and like observations. Howe (1921), investigating the properties of sodium sulphate as a precipitant, demonstrated three zones in which variations of the concentration of the sodium sulphate did not produce any significant change in the amount of protein precipitated. These lay between 13.5 and 14.5 per cent, between 16.4 and 17.4 per cent, and between 21 and 22 per cent, using anhydrous sodium sulphate. This last concentration precipitated approximately the same amount of protein as did half saturation with ammonium sulphate. It was assumed to represent the point at which the globulins had been completely precipitated from solution. The use of the sodium salt for the precipitation enabled the estimation of the residual soluble protein to be carried out by the Kjeldahl technique, and soon the method was adopted widely as a routine procedure in the estimation of the " albumin/globulin ratio." The application of the more delicate physico-chemical techniques to the study of the serum proteins, and in particular the accumulation of data derived from analyses made by the electro-phoretic technique of Tiselius, makes it desirable to check how far the common practical routine methods yield results comparable with those' obtained by the more delicate physico-chemical techniques. Dole (1944) demonstrated clearly that the albumin-globulin ratio of normal plasma calculated from electrophoretic data was constantly at variance with that obtained by the Howe fractionation technique. Subsequently one of the writers, in studying sera from diseased persons, noted not only that there was divergence but that the discrepancy was on occasion such as to suggest that the cruder technique was yielding meaningless results in terms of the electrophoretic data. have been exercised by the same problem. If the routine procedure of reporting the albumin/globulin ratio was to retain any meaning at all it seemed highly desirable to adopt a procedure which, while simple enough for routine …