title: Hepatic oxidative stress following prolonged sublethal microcystin LR exposure.
abstract: Microcystin LR (MCLR) is a naturally occurring protein phosphatase inhibitor and potent hepatotoxin produced by strains of Microcystis aeruginosa. Although its acute toxicity has been well characterized, little is known about its chronic effects. In this study, we sought to acquire evidence that oxidative stress may play a role in the pathogenesis of prolonged sublethal MCLR toxicity. Twelve rats (3 per group) weighing on average 185 g were exposed to 1 of 3 different concentrations of MCLR (16, 32, and 48 microg/kg/day) or to saline via intraperitoneal osmotic pumps for 28 days. Histologic evidence of dose-dependent hepatic inflammation was seen, including infiltration of centrilobular regions by lymphocytes, macrophages, and neutrophils, centrilobular fibrosis, apoptosis, and steatosis. Analysis of lipid peroxidation products revealed a dose-dependent increase in malondialdehyde concentrations with an approximate 4-fold increase in the livers of the high-dose rats over those of the saline-treated controls. Livers from MCLR-exposed rats were more sensitive than those of controls to the cytotoxic effects of the organic oxidizing agent tert-butyl hydroperoxide, based on an MTT (3-[dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) viability assay. These histopathologic and biochemical findings indicate that oxidative stress may play a significant role in the pathogenesis of chronic MCLR toxicosis.
authors.affiliation: Department of Veterinary Pathobiology, University of Illinois, Urbana 61802, USA.
authors.forename: R E
authors.initials: RE
authors.lastname: Guzman
authors.forename: P F
authors.initials: PF
authors.lastname: Solter
mesh_terms: D000410:Alanine Transaminase / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001219:Aspartate Aminotransferases / Q000187:drug effects / Q000378:metabolism; D001427:Bacterial Toxins / Q000633:toxicity; D001835:Body Weight / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000633:toxicity*; D015227:Lipid Peroxidation / Q000187:drug effects; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008297:Male; D008387:Marine Toxins; D052998:Microcystins; D018384:Oxidative Stress / Q000187:drug effects*; D010456:Peptides, Cyclic / Q000633:toxicity*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D001427:Bacterial Toxins; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase; D010749:Phosphoprotein Phosphatases; C057862:cyanoginosin LR