Immunoelectron Microscopic Localization of Peroxisomal Enzymes in the Fibrillar Structures of Rat Liver Peroxisomes Induced by Administration of Acetylsalicylic Acid.

Abstract

Administration of acetylsalicylic acid (ASA) to rats caused an alteration in intraperoxisomal localization of enzymes in liver peroxisomes as investigated by means of immunoelectron microscopy. Rats were fed on a diet containing 0.5% ASA for 2 weeks and livers were fixed by perfusion. Vibratome sections of the liver tissue were processed to routine electron microscopy (EM), alkaline 3, 3′-diaminobenzidine (DAB) reaction for catalase, and post embedding immunocytochemistry for several peroxisomal enzymes. By light microscopy (LM) of the DAB stained materials, many large spindleform peroxisomes were noted in the cytoplasm of hepatocytes, among which normal size of peroxisomes was also observed. By EM, such large peroxisomes contained fibrillar inclusions in the matrix in addition to the crystalloid core. The fibrillar inclusions were more strongly stained than the matrix after the DAB reaction for catalase. By postembedding immunoelectron microscopy, gold particles showing catalase, acyl-CoA oxidase, L-α-hydroxy-acid oxidase A and serine: pyruvate/glyoxylate aminotransferase (SPT) were closely associated with the fibrillar structures. Urate oxidase was confined exclusively to the crystalloid core, on which a few gold particles showing L-α-hydroxy-acid oxidase A was also noted. D-amino acid oxidase was associated exclusively with a clear spot located adjacent to the crystalloid core. In this clear spot, no other enzymes examined were present. The results show that the fibrillar structure induced by ASA includes at least catalase, acyl-CoA oxidase, L-α-hydroxy-acid oxidase A and SPT, but not urate oxidase and D-amino acid oxidase. D-amino acid oxidase is one of elements that constitute the clear spot. Taken together, the present results demonstrate that some subcompartments exist in the experimentally altered liver peroxisomes.