A LIGHT‐SCATTERING TECHNIQUE FOR THE STUDY OF THE PERMEABILITY OF RAT BRAIN SYNAPTOSOMES IN VITRO

Abstract— (1) Swelling of synaptosomes was measured spectrophotometrically by recording changes in extinction at 520 nm. (2) Synaptosomes behaved as osmometers in NaCl solutions. When the tonicity of the medium was changed, synaptosome volume changed in accordance with Boyle and van't Hoff's Law. These changes were reversed on restoring the tonicity of the medium. (3) The rate at which a solute entered the synaptosome was determined from the rate of swelling in the presence of that solute. Permeability of synaptosomes to non‐electrolytes was in the order glucose ≪ glycerol < thiourea = formamide < propylene glycol = dimethylsulphoxide. (4) Synaptosomes were freely permeable to ammonium and acetate ions and impermeable to Ca²⁺, Mg²⁺, PO₄²⁻, SO₄²⁻ and oxalate ions.