UPTAKE OF α-METHYL-D-GLUCOSIDE BY SYNAPTOSOMES FROM RAT BRAIN

Influx of α-methylglucoside into synaptosomes prepared by differential and Ficoll density gradient centrifugation was studied to determine whether this sugar could be used as a model for glucose transport in nerve endings. The rate of uptake of a-methylglucoside was linear over a wide range of substrate concentrations. Influx was only slightly inhibited (12–15%) in the presence of glucose, 2-deoxyglncose, phloretin and 2,4-dinitrophenol and was unaffected by galactose or phlorizin. Conver- sion of a-methylglucoside to phosphorylated intermediates in synaptosomes was negligible. The data are consislent with the influx of a-methylglucoside being primarily a diffusion process or being mediated by a system with an extremely high K_m. However, it is possible that a small portion of the sugar may be transported by the low affinity glucose transport system. The results indicate that a-methylgluco- side is not a good model for glucose transport in synaptosomes as it is in other tissues.