ToxSci Advance Access originally published online on March 31, 2004
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Toxicological Sciences 79, 147-156 (2004)
Toxicological Sciences vol. 79 no. 1 © Society of Toxicology; all rights reserved.
Ortho-Substituted but Not Coplanar PCBs Rapidly Kill Cerebellar Granule Cells
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* University at Albany, School of Public Health, Department of Environmental Health and Toxicology, University at Albany, Rensselaer, New York 12144; Wadsworth Center for Laboratories and Research, New York State Department of Health, and School of Public Health, University at Albany, Albany, New York 12201; and University at Albany, Institute for Health and the Environment, and School of Public Health, Department of Environmental Health and Toxicology, Rensselaer NY 12144
Received November 19, 2003; accepted February 20, 2004
Several PCB congeners were assessed for their cytotoxicity on cerebellar granule cells in an attempt to compare their structure-activity relationship as potential neurotoxicants and to assess the mechanisms associated with their toxicity. Flow cytometry was used to monitor the changes of a number of biochemical endpoints: membrane integrity, intracellular free calcium concentration ([Ca2+]i), reactive oxygen species (ROS) production, mitochondrial membrane potential (
m), and cell size. The non-coplanar, ortho-substituted congeners, PCB 8 (2,4'-dichlorobiphenyl), PCB 28 (2,4,4'-trichlorobiphenyl), PCB 47 (2,4,2',4'-tetrachlorobiphenyl), and PCB 52 (2,5,2',5'-tetrachlorobiphenyl) (10 µM) killed neurons to different degrees within 30 min. Loss of viability was accompanied by increased [Ca2+]i and decreased m. No significant changes of ROS level were observed during exposure. The coplanar congeners, PCB 77 (3,4,3',4'-tetrachlorobiphenyl), PCB 80 (3,5,3',5'-tetrachlorobiphenyl), and PCB 81 (3,4,5,4'-tetrachlorobiphenyl) (10 µM), had no effects on membrane integrity, [Ca2+]i or m in this time period of exposure. In Ca2+-free Tyrode's medium, there was no [Ca2+]i increase after exposure to the ortho-substituted congeners, but also no reduction in loss of membrane integrity, suggesting Ca2+ influx was not the cause of viability loss. The mitochondrial uncoupler, carbonyl cyanide m-chlorophenyl hydrazone (CCCP) (1–2 µM), caused a large decrease of m, but only a slight loss of viability, which suggested that m is not the primary cause of PCB 52-induced cell death. These studies show that ortho-substituted PCBs are toxic to cerebellar granule cells; however, their toxic action is not secondary to elevation of intracellular calcium, a change in mitochondrial membrane potential, or free radical generation.
Key Words: PCBs; flow cytometry; cerebellar granule cells; intracellular calcium concentration; viability; membrane integrity.