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Elke Dopp,^1,2 Ludwig Jonas,³ Barbara Nebe,⁴ Axel Budde,⁴ and Eberhard Knippel⁴

¹Department of Biology, Institute of Cell Physiology and Biosystems Technology, University of Rostock, Rostock, Germany; ²Institute of Hygiene and Occupational Health, University of Essen, Essen, Germany; ³Department of Pathology, ⁴Department of Internal Medicine, University of Rostock, Germany

Abstract

Asbestos induces cytogenetic and genotoxic effects in cultured cell lines in vitro. For further investigations of the fiber-induced cellular changes, electrorotation (ROT) measurements can be used to determine early changes of surface properties and dielectric cellular changes. In the present study, human mesothelial cells (HMC) were exposed to nontoxic concentrations of crocidolite asbestos (1 µg/cm²) for 12, 24, 30, 50, and 72 hr, and were investigated for changes in dielectric properties, morphologic and biochemical changes using ROT measurements, electron microscopy, and flow cytometry, respectively. The results of ROT measurements revealed slightly increased internal conductivity and decreased membrane conductance of HMC during the first 12 hr of exposure to crocidolite. This may be due to functional changes of ion channels of the cellular membrane. However, after exposures of >= 30 hr, reduced internal conductivity and increased membrane conductance of HMC occurred. These effects may be caused by permeabilization of the cell membrane and the leakage of ions into the surrounding medium. The membrane capacitance of HMC is always decreased during exposure of cells to crocidolite fibers. This decreased membrane capacitance may result from the observed reduction in the number of microvilli and from the shrinkage of cells as observed by electron microscopy and flow cytometry. Changes in composition of the plasma membrane were also observed after the labeling of phosphatidylserines (PS) on the cell surface. These observed changes can be related to apoptotic events. Whereas during the first 50 hr of exposure only a small number of HMC with increased exposure of PS on the cell surface was detected by flow cytometry, the dielectric properties of HMC showed marked changes during this time. Our results show that surface property changes of the cellular membrane of HMC as well as interior dielectric changes occur after the exposure of cells to crocidolite fibers. The observed changes are discussed in terms of complex combined cellular effects after amphibole asbestos exposure. Key words: apoptosis, crocidolite, electron microscopy, electrorotation, flow cytometry, phosphatidylserine, plasma membrane. Environ Health Perspect 108:153-158 (2000) . [Online 10 January 2000]

http://ehpnet1.niehs.nih.gov/docs/2000/108p153-158dopp/ abstract.html

Address correspondence to E. Dopp, Universität Essen, Universitätsklinikum, Institut für Hygiene und Arbeitsmedizin, Hufelandstraße 55, 45147 Essen, Germany. Telephone: 49 0201 723 4578. Fax: 49 0201 723 4546. E-mail: elke.dopp@uni-essen.de

We thank J. Saedler, B. Gnich, and I. Poser for excellent technical assistance ; P. Emmerich, M. Barten, J. Zendeh, and T. Heller for obtaining ascites fluid ; and Q. Rahman, D.G. Weiss, and D. Schiffmann for critical reading of the manuscript. We also thank E. Schwarz and G. Fulda for preparation and support in analysis of the electron microscopic samples, respectively.

This work was supported by DFG (Deutsche Forschungsgemeinschaft) grant no. Kn. 385/1-2, the Medical Faculty of the University of Rostock (FORUN-Programme 1997) , and the Kultusministerium of Mecklenburg/Vorpommern (HSP III) .

Received 1 June 1999 ; accepted 2 September 1999.