title: Catalase-negative peroxisomes: transient appearance in rat hepatocytes during liver regeneration after partial hepatectomy.
abstract: Using light microscopy enzyme cytochemistry to localize catalase activity in peroxisomes, a population of peroxisome-negative hepatocytes was detected in livers of rats during liver regeneration induced by two-thirds partial hepatectomy. However, examination by electron microscopy revealed that this population of hepatocytes contained peroxisomes with a delimiting membrane and a nucleoid, but no cytochemically demonstrable catalase activity within their matrix. Regenerating livers 6, 18, 24, 36, 48 and 72 hours, and 1 week after partial hepatectomy showed hepatocytes without catalase activity. However, their numbers varied, with the most numerous appearing at 24 hours after partial hepatectomy. Mitosis of catalase-negative hepatocytes were seen along with mitosis of hepatocytes containing the normal complement of catalase-positive peroxisomes. The catalase-negative hepatocytes did not show evidence of apoptosis or necrotic cell death. Lysosomal acid phosphatase activity and bile canalicular ATPase activity were present in hepatocytes with catalase-negative peroxisomes. Another population of hepatocytes with a small number of catalase-positive peroxisomes appeared and were more numerous at 36 hours after partial hepatectomy; ultrastructurally, these hepatocytes contained both catalase-negative peroxisomes, which appeared to undergo dissolution, and catalase-positive peroxisomes, which were smaller in size. After complete restoration of the liver, all hepatocytes displayed essentially uniform numbers of catalase-positive peroxisomes. These studies indicated that during liver regeneration there is a transient loss of catalase in peroxisomes of some hepatocytes. These cells proliferate and with time acquire new catalase-positive peroxisomes. The observations are discussed in relation to peroxisome biogenesis, hepatocellular carcinogenesis, and oxidative stress during liver regeneration.
authors.affiliation: Department of Pathology, Albert Einstein College of Medicine, Bronx, New York 10461.
authors.forename: I
authors.initials: I
authors.lastname: Oikawa
authors.forename: P M
authors.initials: PM
authors.lastname: Novikoff
mesh_terms: D000818:Animals; D002374:Catalase / Q000378:metabolism*; D006498:Hepatectomy / Q000379:methods; D007150:Immunohistochemistry; D008099:Liver / Q000166:cytology* / Q000201:enzymology* / Q000648:ultrastructure; D008115:Liver Regeneration / Q000502:physiology*; D008297:Male; D008830:Microbodies / Q000201:enzymology*; D008854:Microscopy, Electron; D051381:Rats; D011916:Rats, Inbred F344; D013997:Time Factors
chemical_list: D002374:Catalase