Abstract
Partially hydrolyzed preparations of the bacterial polysaccharide, dextran, have been shown to be useful as non-toxic, osmotically active agents for expanding plasma volume in animals and human beings( 1 - 3 ). These “derived dextrans,” which are relatively unbranched α-1, 6-glucosido-compounds( 4 ) are foreign to the body, and there is still much to be learned about their fate after injection. This paper describes a simple method for the quantitative determination of dextran in biological fluids, which is believed to be superior to the earlier methods of Hint and Thorsen( 5 ) and Klevas( 6 ). It is based on the fact that dextran, like other polysaccharides and unlike the simple sugars, is resistant to digestion with hot alkali and can be precipitated with ethanol.
Method. One ml of plasma, serum, whole blood, or urine is mixed with 3 ml of 30% potassium hydroxide in a 40 ml centrifuge tube, and the mixture is digested for 1 hour in a boiling water bath. Eight ml of water are added to the digested mixture, and the polysaccharide is precipitated by the addition of 20 ml of 95% ethanol, with thorough mixing. Complete precipitation of the dextran is assured by at least 3 hours' storage of the ethanol-treated mixture in a refrigerator. The precipitate is collected by centrifugation at 2500 r.p.m. for 25 minutes, and the supernatant is decanted. When whole blood is used, it is necessary to reprecipitate the polysaccharide. The precipitate is dissolved in 5 ml of water and transferred quantitatively to a volumetric flask. A final dilution is chosen such that 1 ml of solution contains from 10 to 100 μg of polysaccharide. Dextran is determined in duplicate samples of this solution, using the anthrone reagent in a method described elsewhere( 7 ). A standard glucose solution may be used, the results being expressed in glucose equivalents.
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