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Title:Toxicopathology of microcystin-LR in vivo and in vitro
Author(s):Hooser, Stephen Blair
Doctoral Committee Chair(s):Haschek, Wanda M.
Department / Program:Pathobiology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Health Sciences, Pathology
Health Sciences, Public Health
Biology, Veterinary Science
Abstract:Microcystin-LR (MCLR), produced by the blue-green alga Microcystis aeruginosa, causes death of livestock and is a public health hazard. The mechanism of MCLR toxicity was investigated using the rat. Changes in serum chemistry parameters and morphology caused by MCLR were characterized in vivo and in vitro. The uptake and subcellular localization of tritiated-MCLR were determined in rat hepatocytes and perfused rat livers.
A steep dose-response lethality curve was seen with MCLR. Rats and mice were clinically unaffected or were clinically affected and died. Histologic hepatic lesions, beginning at 20 min, consisted of disassociation of centrilobular hepatocytes which progressed to severe hemorrhage and necrosis. In the rat, intact hepatocytes were present in pulmonary capillaries. Mice survived 60 to 90 min postdosing while rats survived 24 to 32 hrs.
In rats, initial ultrastructural changes consisted of widening of hepatocyte intercellular spaces. At 20 min, there was invagination of hepatocyte plasma membranes, formation of intracytoplasmic vacuoles, loss of microvilli, and pronounced hepatocyte separation. By 60 min there was breakdown of endothelium, hemorrhage and hepatocyte necrosis. Hepatocellular debris was present in pulmonary and renal capillaries.
In suspension, rat hepatocytes but not non-parenchymal cells had plasma membrane blebbing. In monolayer hepatocyte culture, MCLR caused plasma membrane blebbing which was associated with aggregation of rhodamine-stained filamentous actin. Alterations in hepatocyte actin filaments were distinct from those caused by phalloidin and cytochalasin B.
The uptake of $\sp3$H-MCLR was rapid in suspensions of rat hepatocytes and perfused livers. Incubation of hepatocytes at 0$\sp\circ$C or with rifampicin greatly reduced and slowed the uptake, suggesting that $\sp3$H-MCLR uptake may be via an energy dependent bile acid carrier which may be hepatocyte-specific. Subcellular fractionation showed that 65 to 77% of the radiolabel localized in the cytoplasmic fractions. Radiolabel did not appreciably associate with the insoluble fraction (containing actin) following detergent extraction. Greater than 50% of the radiolabel was present in the TCA precipitate indicating that $\sp3$H-MCLR may associate with cytoplasmic protein.
Issue Date:1989
Rights Information:Copyright 1989 Hooser, Stephen Blair
Date Available in IDEALS:2011-05-07
Identifier in Online Catalog:AAI8924840
OCLC Identifier:(UMI)AAI8924840

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