The characteristics of arginine transport by rat cerebellar and cortical synaptosomes

The uptake of L-[3H]arginine into synaptosomes prepared from rat cerebellum and cortex occurred by a high-affinity carrier-mediated process. The uptake of arginine appeared to be potentiated by removal of extracellular Na+, inhibited by high levels of extracellular K+, but not by depolarization with veratridine or 4-amino pyridine. The effect of Na+ removal or K+ elevation did not seem to be due to changes in intracellular Ca2+ or pH. In both brain regions, uptake was significantly inhibited by L-arginine, L-lysine, L-ornithine, and L-homoarginine, but not by D-arginine nor L-citrulline. Uptake was also inhibited by NG-monomethyl-L-arginine acetate, but not by NG-nitro-L-arginine methyl ester nor NG-nitro-L-arginine except in the cortex at a concentration of 1 mM. The results indicate that the carrier system operating in synaptosomes showed many of the characteristics of the ubiquitous y+ system seen in many other tissues, although its apparent sensitivity to variations in extracellular Na+ was unusual.