The phlorizin effect on the transport of sugars at the antiluminal face of teased flounder tubules

Abstract

The effect of phlorizin on the uptake of sugars by teased renal tubules of the flounder (Pseudopleuronectes americanus) and slices of rabbit kidney cortex was investigated: 1. Increasing concentrations (0.05-0.5 mM) of phlorizin inhibited the uptake of D-glucose at the antiluminal face of the tubular cells by affecting primarily the cellular levels of glucose phosphates, whereas the levels of free glucose remained constant. This result suggests the possibility that the actual transport step is associated with sugar phosphorylation. 2. As opposed to the high affinity of phlorizin for the Na+-dependent active transport system for methyl-alpha-D-glucoside in flounder and rabbit kidney, the carrier shared by glucose, 2-deoxyglucose and mannose at the antiluminal face of tubular cells displays a low affinity for the inhibitor. It is suggested that glucose and its C2-analogs enter the renal tubular cells at the antiluminal face by a phosphorylating pathway which has a low affinity for phlorizin, and mix readily with the metabolic pool. This transport pathway serves the nutritional requirements of the cells.