Abstract
Jolliffe, Shannon and Smith 1 have presented evidence that the excretion of xylose and other non-metabolized sugars can be used to measure glomerular filtration in the dog, and by simultaneous xylose and creatinine clearances they have demonstrated the tubular secretion of creatinine in that animal. The use of xylose for measuring glomerular filtration has been confirmed by Clark and Smith 2 in the elasmobranch, Squalus acanthias and by Marshall 3 in the frog, Rana catesbiana.
A comparison of the excretion of xylose and creatinine in man is of particular interest, since the latter substance has been widely used on RehbergV recommendation as a measure of glomerular filtrate.
The subjects of this investigation were healthy, male, medical students between the ages of 20 and 30; xylose, creatinine and urea clearances were measured in the morning after no breakfast or a light meal in which milk, tea, coffee and protein were excluded.
Xylose (50 gm.) and creatinine (10 gm.) were administered separately with varying amounts of water 90 and 60 minutes respectively prior to the start of the first urine collection period. Three or more consecutive 20-minute periods were observed; in most of these the rate of urine flow was above the lower figure (1.7) given as the augmentation limit of urea. 5 Blood samples were withdrawn at 30-minute intervals and plasma concentrations were interpolated to the middle of each urine period. Plasma and urine (diluted to the expected U/P ratio) were analyzed by the methods described by Shannon, Jolliffe and Smith. 6
The average clearances (UV/P.S.A.) expressed as cc. per minute per square meter of body surface are: urea, 35.1; xylose, 51.3, and creatinine, 89.1. The average creatinine/xylose ratio was 1.74, and the average urea/xylose ratio was 0.684.
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