Stabilization of ascorbic acid and norepinephrine in vitro by the subcellular fractions of rat cerebral cortex

The effect of various subcellular fractions of rat cerebral cortex on the autoxidation of ascorbic acid and norepinephrine in a physiological salt solution, pH 7.4, was investigated. The rate of the two reactions was determined spectrophotometrically at 265 and 480 nm, respectively. The cytoplasmic, microsomal, crude mitochondrial fractions and a soluble phase of mixed subcellular origin (100,000 g supernatant) were tested in an assay system in which the final dilution of the cellular components was in the 10(3) to 10(6) range. The samples were heat-treated (30 min at 100 degrees C) and dialyzed (50,000 mol.wt. cut-off) prior to analysis. The preparations produced approximately 80% inhibition at 10(3)-fold dilution and marginal inhibition at 10(5)-fold dilution, except the microsomal preparation, which was a considerably weaker inhibitor in the norepinephrine autoxidation test. The study shows that all three major subcellular compartments of the rat cerebral cortex have macromolecules with a high level of heat-stable autoxidation-inhibiting activity.