Isolation of peroxisomes from rat liver using sucrose and Percoll gradients.

Peroxisomes were isolated from the livers of both control and clofibrate-treated rats. Two procedures, one with a sucrose gradient, and a second with Percoll gradients, were utilized. The Percoll procedure allowed contamination of the isolated peroxisome fraction on protein basis, by lysosomes (8%), by mitochondria (5%) and by microsomes (2%). The peroxisome fraction isolated by the sucrose gradient showed no significant contamination with mitochondria, but the fraction contained 13% microsomes. In addition to established peroxisomal enzymes, the isolated peroxisomes also contained cytochrome b5, NADH-cytochrome c reductase and NADPH-isocitrate dehydrogenase. The peroxisomal membranes were also separated from the content, and they were found to have a relatively high phospholipid/protein ratio (0.55).