Abstract
Effect of exogenous D-glucose on oxygen consumption (QO2) was investigated in the proximal tubules of the Triturus kidney. In the proximal tubule, which was perfused and incubated with a solution containing Na+, QO2 was increased dependently of the concentration of added glucose. By removal of Na+ from the perfusate and incubation solutions, QO2 kept the level even by increasing adding glucose. The glucose dependence of QO2 in the proximal tubule showed the saturable manner of a Michaelis-Menten type and gave a half saturation concentration of 1.3mM. When phlorizin (1×10-3M) or ouabain (1×10-3M) was added to the perfusate and incubation solutions, the glucose dependency of QO2 was abolished, even in the Na+-containing solution. When α-methyl-D-glucoside (α-MG) was used instead of D-glucose, the QO2 of the proximal tubule showed a dependency on the concentration of α-MG. On the other hand, when D-mannitol was used instead of D-glucose, the QO2 was independent on the concentration of D-mannitol. The increase in QO2 of the proximal tubule by exogenous D-glucose could be explained by the stimulation of the Na+ pump, which is the consequence of enhanced Na+ entry through Na+/D-glucose cotransport across the luminal membrane.
