Phosphate Ion Transport in Rabbit Brain Synaptosomes

: Synaptosomes (vesicles of nerve endings) isolated from rabbit brain were studied as a model system for the uptake of inorganic phosphate. The phosphate uptake showed a sodium-dependent, saturable component with a Kt of 0.29 mm, The sodium-dependent component was larger at pH 6 than at pH 7.4 or 8. Application of potassium salts, ouabain, monensin, nigericin or FCCP decreased the uptake. The results indicate that the sodium-sensitive phosphate influx is dependent on the Na+ gradient and on the membrane potential, which might act, preferentially, on the transport of the monovalent phosphate ion.