D‐galactose Transport by Synaptosomes Isolated From Rat Brain

Synaptosomes prepared by differential and Ficoll density gradient centrifugation took up d ‐galactose by two saturable transport systems: one. a high affinity system with a K m of 0‐25 mn and V max of 075 nmol/mg protein 3 min, the other, a low affinity system with a K m of 47 mM and a V max of 135 nmol/mg protein/3 min. The high affinity system was inhibited by 1‐5 mM phlorizin but was unaffected by the absence of sodium ion or the presence of 1 mM ouabain. The low affinity system was unaffected by phlorizin or ouabain. Both systems were inhibited by high concentrations of glucose. 2‐deoxyga‐lactose. and inositol, and by 2.4‐dinitrophcnol. Galactose was rapidly converted in synaptosomes to phos‐phorylatcd intermediates and was more slowly oxidized to 14 CO 2