D Glucose enhancement of water reabsorption in proximal tubule of the rat kidney

Water reabsorption in the proximal convoluted tubule of the rat kidney was examined by in vivo microperfusion techniques in order to examine the effect of D glucose within the tubular lumen. When tubules were perfused with a balanced artificial solution containing Na, K, Cl, HCO₃, urea, and D glucose, absolute reabsorption averaged 4.01±0.24 nl/min per mm tubule length. Perfusion with isotonic NaCl resulted in a 37% decrease in reabsorption of 2.54±0.17 nl/min per mm. Addition of D glucose to the NaCl perfusate enhanced water reabsorption to values similar to those obtained with the balanced artificial perfusate. The enhanced water reabsorption consequent to the addition of D glucose to the NaCl perfusion solution was completely inhibited by addition of phloridzin to the perfusate. The addition of an unabsorbed hexose, 2 deoxy D glucose, to the NaCl perfusate failed to enhance water reabsorption, whereas the addition of an incompletely reabsorbed sugar that is not metabolized, 3 O methyl D glucose, resulted in partial enhancement of the absolute rate of water reabsorption. These studies demonstrate that D glucose has the specific effect of augmenting water reabsorption in the proximal tubule of the rat kidney.