Renal Excretion of Galactose in Man, with Determination of the Maximal Tubular Reabsorption for Galactose

Abstract

The urinary excretion of galactose and glucose was determined in ten patients during periods of constant arterial plasma concentration of galactose, obtained by continuous intravenous infusion. The relationship between excretion rate and plasma concentration of galactose indicated that no renal threshold for galactose exists. The tubular reabsorption of galactose was studied as a function of the plasma concentration and the glomerular filtration rate, assuming galactose to be freely filtered in the glomeruli, and not excreted in the tubuli, but reabsorbed in a rate-limited system. The maximum reabsorption of galactose was calculated to be 1.22 mg per ml of filtrate (95% confidence interval: 0.88–2.00 mg/ml). The ‘affinity’ constant of the reabsorption process was estimated to be 1.37 mg/ml (95% confidence interval: 0.99–2.00 mg/ml). Indications were found of competition between galactose and glucose for a common tubular reabsorption mechanism.

Key Words:

• Biological transport
• galactose
• kidney tubules