A Study of the Blood Glutathione

Since the discovery and isolation of glutathione from tissues by Hopkins (7) several methods have been elaborated for its quantitative determination in tissue extracts. The basic principle of all the methods in common use is the oxidation of the sulfhydryl grow, -SH, to the disulfide group, S-S, by a measurable amount of oxidant. Obviously these methods include the determination of sulfhydryl compounds other than glutathione, but since this substance is present in relatively large amounts, the results are preferably expressed in terms of it. Thioneine, for instance, which is also a sulfhydryl compound, is present in blood in quantities of 4.2 to 15 mg. (1). Free cysteine is apparently absent from blood (6). The amount of glutathione, on the other hand, has been variously estimated by different investigators, the values obtained by different methods ranging from 20 to 90 mg. per 100 cc. of blood. These widely differing figures seem to indicate that there are variations between the methods used. Without recovery experiments the reliability and validity of a method appear questionable. In a recent paper Gabbe (4) has given an interpretation of the different results obtained by three different methods applied to one and the same specimen of blood. The present study is concerned first, with qualitative tests of a large number of blood filtrates and, second, with quantitative determination of reduced glutathione with a calorimetric method recently published by Mason (9).