Isolation of rat liver lysosomes by a single two-phase partition on dextran/polyethylene glycol

Crude mitochondria from liver rats were added to a two-phase system containing dextran and polyethylene glycol. The polymer and ionic concentration values of the two-phase system were changed in order to separate lysosomes from mitochondria. The best separation of lysosomes and mitochondria was obtained at 6.6-6.6% (w/w) dextran-polyethylene glycol and 5 mmol/kg ammonium chloride as shown by enzyme assays. This procedure showed good reproducibility, and lysosomes were never contaminated with more than 16% mitochondria, as determined by succinate dehydrogenase activity, and beta-D-galactosidase and acid phosphatase activities were enriched five- to sixfold. The lipid composition profile of lysosomes was quite similar to that obtained by means of free carrier electrophoresis, considered a reference method.