High and low affinity transport of L-arginine in rat brain synaptosomes

The uptake of L-arginine into purified rat brain synaptosomes was investigated with respect to time and various concentrations of L-[3H]arginine. Specific uptake was found to be linear with time for up to 5 min of incubation at 37 degrees C. Electrolytes, including sodium chloride, potassium chloride, magnesium chloride and calcium chloride, inhibited uptake of 3 microM L-arginine, and the inhibitory effect increased with increased electrolyte concentration under constant osmolarity. It was found that L-arginine was transported into synaptosomes by two uptake components--a high affinity component (3.5 microM) and a low affinity component (100 microM). These two components were similar to the Ly+ system because of their extreme sensitivity to inhibition by L-lysine and L-ornithine but were distinguishable from each other by kinetic analysis of the uptake data and by their relative sensitivity to inhibition by several amino acids.