PRESENCE OF HETEROGENEOUS PEROXISOMAL POPULATIONS IN THE RAT NERVOUS-TISSUE

Peroxisomes were purified from the nervous tissue of 14-day-old rats b y means of a Nycodenz gradient. Peroxisomal enzymes exhibited differen t sedimentation patterns: dihydroxyacetone phosphate acyl-transferase equilibrates at 1.142 g/ml together with the first peak of catalase; p almitoyl-CoA oxidase and D-amino acid oxidase activities are mainly re covered at 1.154 g/ml; the second peak of catalase is found at 1.175 g /ml. Morphological and semi-quantitative analyses of immunogold-labell ed peroxisomes reveal profound heterogeneity of the particles. Very sm all (= 0.2 mu m diameter), electron dense vesicles containing catalase or thiolase, but devoid of other tested enzymes, are preferentially f ound in the light region, together with larger (> 0.2 < 0.3 mu m) and less electron dense palmitoyl-CoA oxidase-positive peroxisomes, At int ermediate density (1.154 g/ml) peroxisomes of more uniform size (0.25- 0.27 mu m), containing palmitoyl-CoA oxidase or thiolase with or witho ut catalase are preferentially found. This population extends toward t he densest region of the gradient, where very large D-amino acid oxida se-containing peroxisomes are also found. In this region, smaller pero xisomes, often polymorphic, which are catalase- and thiolase-positive and D-amino acid oxidase/palmitoyl-CoA oxidase-negative, are also obse rved. The possibility that the heterogeneity of neural peroxisomes may reflect both cellular heterogeneity and ongoing peroxisomal biogenesi s is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.