Renal Clearance of Glucosamine in the Rat. ∗

Abstract

Discussion and summary

That the clearance of exogenous glucosamine in the rat occurs at the same rate as that of inulin suggests that glucosamine might be a substance which after glomerular filtration does not undergo subsequent tubular reabsorption or secretion. The inability to change the renal clearance of glucosamine after elevation of plasma glucosamine concentrations from approximately 2 to 70 mg% indicates that excretion of glucosamine is probably independent of tubular secretion or reabsorption.

Renal excretion of glucosamine in dogs was shown by Carter and Peters to be only by glomerular filtration. The clearance of glucosamine was identical to that of creatinine, and glucosamine did not interfere with the glucose reabsorption (glucose Tm) or with the secretion of N‘-methylnicotinamide by the dog or chicken kidney tubule(2).

Equilibrium dialysis experiments showed that glucosamine was not bound to plasma proteins(2). Attempts to determine endogenous glucosamine or other hexosamine by the Dische and Borenfreund method in plasma and urine samples of 3 normal non-perfused rats revealed that endogenous glucosamine levels are not measurable by this method. Therefore, in view of the above and the fact that Coulson and Hernandez(3) found that glucosamine excreted by the rat kidney was not a metabolic product, the glucosamine clearances do not require correction for any of these factors; i.e., plasma binding, endogenous levels, or metabolism of the glucosamine.

Glucosamine appears to be another substance in addition to inulin that can be used accurately to measure glomerular filtration rate in the rat.