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Howard E. Wey,* David P. Conover, Patty Mathias, Mark Toraason, and W. Greg Lotz

The National Institute for Occupational Safety and Health, Cincinnati, Ohio, USA

Abstract

An effect on intracellular calcium continues to be proposed as a biochemical pathway for the mediation of biologic effects of electrical-power-frequency magnetic fields (MF) . However, reproducible results among laboratories are difficult to attain and the characteristics of magnetic field effects on intracellular free calcium ([Ca²⁺]_i) are not well understood. We attempted to repeat the studies of Lindström et al. [Intracellular Calcium Oscillations in a T-Cell Line by a Weak 50 Hz Magnetic Field. J Cell Physiol 156:395-398 (1993) ] by investigating the effect of a 1.5-G 50-Hz MF on [Ca²⁺]_i in the Jurkat lymphocyte T-cell line. Changes in [Ca²⁺]_i were determined using microscopic imaging of fura-2 loaded Jurkat cells on poly-l-lysine-coated glass coverslips. The MF was generated by a single coil constructed with bifilar wire and located in the same plane as the cells. Cells were randomly exposed for 8 min to MF, sham field (SF) , or no field (NF) conditions. The exposure condition remained coded until data analysis was complete. Each exposure period was preceded by an 8-min data collection to establish a baseline for [Ca²⁺]_i. After each exposure condition, cells were exposed to anti-CD3 antibody that induced a rapid increase in [Ca²⁺]_i in responsive cells ; this provided a positive control. [Ca²⁺]_i was analyzed for individual cells as spatially-averaged background-corrected 340/380 nm ratios, and a [Ca²⁺]_i transient was considered significant for positive deviations from baseline of 3 an estimate of noise in the baseline. Typically, 25-50 cells/field were viewed and approximately 50% had no [Ca²⁺]_i transients in the baseline period and also responded to positive control. Only cells responding to positive control and lacking changes in [Ca²⁺]_i during the baseline period were considered qualified for assessment during the exposure period. The incidences of [Ca²⁺]_i transients during the exposure period for two experiments (40 objective) were 16.5, 14.6, and 14.2% for MF, SF, and NF, respectively, and were not statistically significantly different. Previous studies by Lindström et al. [Intracellular Calcium Oscillations in a T-Cell Line after Exposure to Extremely-Low-Frequency Magnetic Fields with Variable Frequencies and Flux Densities. Bioelectromagnetics 16:41-47 (1995) ] showed a high response rate (92%) for exposure to 1.5-G 50-Hz MF when individual cells were preselected for investigation. We found no such effect when examining many cells simultaneously in a random and blind fashion. These results do not preclude an effect of MF on [Ca²⁺]_i, but suggest that responsive cells, if they exist, were not identified using the approaches that we used in this study. Key words: fura 2, intracellular calcium, Jurkat cells, lymphocytes, magnetic fields. Environ Health Perspect 108:135-140 (2000) . [Online 7 January 2000]

http://ehpnet1.niehs.nih.gov/docs/2000/108p135-140wey/ abstract.html

Address correspondence to M. Toraason, National Institute for Occupational Safety and Health (NIOSH) , MS-C23, 4676 Columbia Parkway, Cincinnati OH 45226 USA. Telephone: (513) 533-8207. Fax: (513) 533-8138. E-mail: mht1@cdc.gov

*Current address: H.E. Wey, South Dakota State University, Brookings, SD 57007 USA.

We thank G. Boorman, G. Leikauf, R. Liburdy, D. Lyle, E. Lindström, M. Misakian, J. Putney, R. Savage, J. Snawder, and J. Walleczek for their recommendations and comments during the planning of this research and/or the writing of this report.

This study was supported by the National Institute of Environmental Health Sciences and NIOSH under Interagency Agreement no. YOI-ES-50313 to meet the goals of the electric and magnetic fields Research and Public Information Dissemination Program.

Received 4 March 1999 ; accepted 23 August 1999.