The Renal Clearance of Alkali-Stable Inulin

Abstract

Commercial inulin available at present is not a homogeneous product (1). It consists of two major fractions the proportions of which vary: (a) a portion of relatively large molecular weight resistant to heating in alkali; and (b) a portion of smaller molecular weight susceptible to destruction with alkali. In addition, most samples contain a small percentage of fructose, which also yields color in the analytical methods for inulin unless removed by treatment with yeast or hot alkali.Two recent reports (2, 3) indicate that the clearance of the alkali-stable and alkali-labile fractions of inulin may not be equal. Since some commercial preparations of inulin (such as the one used in this study) may contain as much as 50 per cent of the alkali-labile material, considerable errors in estimation of glomerular filtration rate would occur if a difference in clearance of the two fractions exists.The present report indicates that the clearance of the two fractions is identical, within the limits of error of analysis, in confirmation of the preliminary report by Cotlove (1). METHODSSubjects. The subjects were patients of the National Heart Institute at the Clinical Center. One was a normal volunteer. The others had renal or endocrine diseases. In most cases studies were performed in the fasting state. The comparisons were made during clearance determinations performed for other purposes.Procedure. Before each clearance determination, the ampoules of inulin to be used were mixed together and a portion withdrawn for analysis.' A priming injection and a sustaining infusion of inulin were administered intravenously. The plasma level of the alkali-stable fraction was approximately 13 mg. per cent. After a 30 to 40-minute equilibration period, 3 to 8 urine collection periods were obtained, each of 20 to 40 minutes' duration.

Intrarenal Vascular Sites of Action of Adenosine and Glucagon

“…Renal plasma flow=RBFx (1 -hema tocrit). Inulin was determined by the method of Walser et al (18). To compare the GFR value obtained from the renal extraction of inulin with the GFR value obtained from the urinary excretion of inulin, a polyethylene catheter was inserted into the left ureter for urine collection.…”

Antivenom action on renal effects induced by Thalassophryne nattereri venom

“…Samples of urine and perfusate were collected at 10-minute intervals for analysis of sodium and potassium level by flame photometry; inulin was determined by direct hydrolysis and osmolality was measured in a vapor pressure osmometer (Wescor 5100C, USA) (16). The Thalassophryne nattereri venom and antivenom were preincubated at 37°C for 30 minutes before addition in perfusion system.…”

Attenuation of adrenomedullin‐induced renal vasodilatation by NG‐nitro L‐arginine but not glibenclamide

“…Inulin was determined by colorimetry, as described by Walser et al (1955) and glomerular filtration rate (GFR) was estimated by the inulin clearance. Urinary and plasma concentrations of sodium and potassium were measured by flame photometry (205D, Hitachi, Tokyo, Japan).…”