Specificity of sodium-dependent electrogenic sugar transport in amphibian kidney proximal tubule.

Microelectrode studies were performed to examine the specificity of the electrogenic sugar transport by Triturus proximal tubule. Two types of carriers could be distinguished, one having an affinity for D-mannose but not for D-xylose (M type), and the other having the reverse characteristics (X type). D-Glucose and alpha-methyl-D-glucoside had a relatively high affinity for both types of carriers, but D-galactose, D-fructose, 3-O-methyl-D-glucose, D-mannitol and L-glucose had no affinity for them. The observed structural requirements of renal sugar transport were different from and stricter than those of intestinal sugar transport observed in the same animal.