Abstract
The constancy of the rate of disappearance of xylose from the blood of animals 1 and the change in the rate of elimination after experimental damage to the kidney membrane 2 suggested the possibility of its use as a delicate indicator of damaged renal function. The present availability of xylose would render it an excellent substance for kidney function tests in analogy to the liver function tests which employ such sugars as galactose, levulose, etc. Xylose is particularly suited for this purpose since its elimination is practically independent of the liver.
On the oral administration of 50 gm. of xylose, 25 ± 5% is eliminated by a normal man within 24 hours (Table I) in the urine. The normal kidney can concentrate this substance up to at least 25% within 2 hours. In the blood the non-fermentable reducing substance rises to 80 mg. % within 3 hours, and after 6 hours the normal value of 28 mg. % is approached. (Table II.) These determinations were carried out by the method of Somogyi. 3
On the other hand, in cases of kidney damage the non-fermentable reducing substance in the blood keeps on rising, so that after 6 hours there may be 125 or more mg. % of non-fermentable reducing substance in the blood. The elimination in the urine is much lower, so that figures of 1 to 2 gm. total excretion in 24 hours instead of the normal 12-13 gm. are encountered. The inability of the damaged kidney to concentrate the xylose is particularly striking, so that in cases of severe impairment of renal function, instead of the normal 3% concentration of reducing substance in the urine after 2 hours, we find 0.10% or even less.
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