A Colorimetric Method for the Determination of Inulin in Blood Plasma and Urine by Kurt Steinitz

Of all substances used in the determination of glomerular filtration, inulm is one of the most important. Hendrix, Westfall, and Richards (1) consider it to be the most suitable for the calculation of the filtration rate, because it is the substance with the greatest, molecular weight known so far which is completely filtered through glomerular membrane (Westfall and Landis (2), Bunim, Smith, and Smith (3)). Inulin combines the ideal properties required in a substance used for the calculation of glomerular filtration (Jolliffe, Shannon, and Smith (4)). It is probable that inulin, an inert substance which mixes with the blood and body fluid without penetrating into the cells (Van Slyke, Hiller, and Miller (5)), will also become important in certain other physiological studies. For these reasons it is desirable to have a sensitive and exact quantitative test for the estimation of inulin. So far inulin has been estimated by the difference of reduction before and after hydrolysis of blood plasma filtrate. Fasting blood, however, gives also a difference of reduction before and after hydrolysis. This fasting value must be subtracted from the results obtained. According to Van Slyke, Hiller, and Miller (6) this difference in dogs is always under 5 mg. per cent, calculated as glucose. In man, however, this difference in blood filtrate can attain considerably higher values. With the technique of Van Slyke and his collaborators (S),l values between 3 and 25 mg. per