Glucose transport in isolated rat adipocytes with measurements of L-arabinose uptake.

Data is presented suggesting that rates of L-arabinose transport, calculated from L-[1-14C]arabinose uptake measurements, can be used as indicators of changes in the rates of glucose transport in isolated rat adipocytes. L-[1-14C]arabinose, at 37 degrees C, was found to be nonmetabolizable and taken up by adipocytes exponentially with time reaching 95% of equilibrium in 30 min. When L-arabinose is corrected for background, the corrected uptake values conform to the time-dependent monoexponential uptake relationshiop predicted for a facilitated transport system and are not significantly different from 0 in the presence of 70 micron cytochalasin B. Transport rates were calculated from corrected uptake values near the half-maximal uptake of L-arabinose and from a value of the total amount of L-arabinose in the cell at equilibrium. Competitive inhibition of L-arabinose transport by glucose and countertransport of L-arabinose in the presence of glucose suggest that L-arabinose and glucose share the same transport system. Data is presented demonstrating the effect of insulin and dexamethasone on the transport system that confirms the conclusions obtained by other investigators using other methods.