title: Reversible mitochondrial swelling in cultured rat hepatocytes exposed to 1,2-dimethylhydrazine.
abstract: The early structural changes of F344 rat hepatocytes exposed to the hepatocarcinogen 1,2-dimethylhydrazine (DMH) were characterized in short-term monolayer cultures. Continuous exposure of monolayers to DMH (2-16 mM) caused cytoplasmic vacuoles visible by phase-contrast microscopy in all hepatocytes within 6 hr of exposure. These changes preceded maximal release of lactate dehydrogenase (LDH) which occurred after 48 hr of continuous exposure to cytocidal concentrations of DMH (8-16 mM). Ultrastructurally, hepatocytes exposed to DMH (4 mM, 6 hr) showed a twofold increase in mitochondrial diameter from 340 +/- 70 nm in control hepatocytes to 800 +/- 140 nm in DMH-exposed cells. Hepatocyte monolayers exposed to DMH (4 mM, 6 hr) with subsequent removal of DMH attained normal phase-contrast appearance within 6 hr. Ultrastructural studies showed no significant differences when compared with control hepatocytes and mitochondrial diameters (330 +/- 70 nm) were comparable with control hepatocytes. Pretreatment of hepatocytes with depletors of cellular reduced glutathione concentration, including 1,3-bis(2-chloroethyl)-1-nitrosourea (40 microM) and diethyl maleate (160 microM), did not potentiate hepatocellular vacuolation nor release of LDH from hepatocytes exposed to DMH (0-16 mM, 48 hr). These studies demonstrate a distinctive form of reversible high-amplitude mitochondrial swelling that can be monitored by phase-contrast microscopy of cultured hepatocytes in monolayers. Since DMH-induced mitochondrial swelling and its progression to irreversible injury are not potentiated by depletors of reduced thiols, this response appears distinct from prelethal mitochondrial swelling in hepatocytes subjected to oxyradical-mediated mechanisms of injury.
authors.affiliation: Department of Pathology, University of Guelph, Ontario, Canada.
authors.forename: M S
authors.initials: MS
authors.lastname: Pollanen
authors.forename: B A
authors.initials: BA
authors.lastname: Quinn
authors.forename: G K
authors.initials: GK
authors.lastname: Wollenberg
authors.forename: M A
authors.initials: MA
authors.lastname: Hayes
mesh_terms: D019813:1,2-Dimethylhydrazine; D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D002330:Carmustine / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004127:Dimethylhydrazines / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000648:ultrastructure; D008297:Male; D008298:Maleates / Q000494:pharmacology; D008763:Methylhydrazines / Q000494:pharmacology*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D010873:Pinocytosis / Q000187:drug effects; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: D004127:Dimethylhydrazines; D008298:Maleates; D008763:Methylhydrazines; D007770:L-Lactate Dehydrogenase; C014476:diethyl maleate; D005978:Glutathione; D019813:1,2-Dimethylhydrazine; D002330:Carmustine; D000111:Acetylcysteine