Binding of 3H-gamma-aminobutyric acid and 14C-glycine to synaptosomal-mitochondrial fractions of rat cerebral cortex and spinal cord.

Abstract

The "binding" of γ-aminobutyric acid (GABA) and glycine to subcellular particles of rat cerebral cortex and spinal cord has been studied using differential centrifugation and double-isotope methods. When cerebral cortices and spinal cords were homogenized in isosmotic sucrose solutions containing 40 mM NaCl plus "tracer" amounts of 3H-GABA and 14C-glycine and then subjected to differential centrifugation, 3H-GABA was bound preferentially to particles prepared from cerebral cortex while 14C-glycine was bound to a similar extent to particles of both cerebral cortex and spinal cord. However, when P2 fractions, enriched in synaptosomes and mitochondria, were first isolated using unlabelled Na+-free sucrose solution and then resuspended in solutions containing 40 mM NaCl plus the labelled amino acids, preferential binding of the amino acids occurred. Under these latter conditions 3H-GABA was bound to a greater extent to synaptosomal–mitochondrial particles of cerebral cortex while 14C-glycine was bound to a greater extent to identically prepared particles of spinal cord. Although the retentions of both 3H-GABA and 14C-glycine were increased by allowing the particles to stand at 23 °C for 15 min, preferential binding still existed.