Particules subcellulaires dans les tumeurs: II Analyse de fractions mitochondriales et microsomiales de l'hépatome HW par centrifugation isopycnique

Abstract

1. 1. Mitochondrial and microsomal fractions from a rat transplantable hepatoma have been analysed by isopycnic centrifugation. Experiments were performed with two kinds of gradients, one made with pure aqueous sucrose, the other with glycogen dissolved in aqueous sucrose solutions of different concentrations. 2. 2. After density equilibration in a sucrose gradient of a mitochondrial fraction, cytochrome oxidase shows a relatively homogeneous distribution while acid hydrolases exhibit more flattened distribution curves in higher density regions of the gradient. After isopycnic centrifugation in glycogen gradients, distribution patterns of cytochrone oxidase are quite different from those of acid hydrolases. On the other hand, the equilibrium density of mitochondria and of lysosomes as ascertained respectively from cytochrome oxidase and from acid hydrolases behaviour, is greatly affected by the sucrose concentration of the medium although differently for the two kinds of particles. 3. 3. Isopycnic centrifugation of a microsomal fraction in an aqueous sucrose gradient and in glycogen gradients strongly suggest that glucose- 6-phosphatase and catalase are associated with distinct elements of the microsomal fraction. 4. 4. Comparison of our results with those obtained by de Duve and his co-workers on rat liver [2, 5, 6] suggest that significant differences exist between mitochondria of the hepatoma HW and those of rat liver as well as between structures bearing catalase in both tissues; in contrast, lysosomes seem to be very comparable in the tumour and in the liver.