Study type: Medical/biological study (experimental study)

Increase in radiation-induced HPRT gene mutation frequency after nonthermal exposure to nonionizing 60 Hz electromagnetic fields. med./bio.

Published in: Radiat Res 1999; 151 (4): 489-497

Aim of study (acc. to author)

To explore the question whether a non-thermal 60 Hz magnetic field can enhance the 2 Gy gamma radiation induced hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene mutation frequency.

Background/further details

The hypoxanthine-guanine phosphoribosyl transferase (HPRT) is an enzyme in the purine (for example guanine) synthesis pathway. HPRT-negative cells are not able to use guanine for GTP synthesis und thus, they have to synthesize the base de novo. Using the guanine analog 6-thioguanine HPRT-positive cells use 6-thioguanine for nucleotide synthesis. However, integration of 6-thioguanine leads to DNA and RNA damage and it is lethal for these cells. In contrast, HPRT-negative cells are not able to utilize 6-thioguanine and survive.
The HPRT gene mutation assay is a well-established mutagenicity assay based on the selection of clones resistant to the purine analog 6-thioguanine. I.e. for determination of the induction of 6-thioguanine resistant mutation in the HPRT gene exposed cells are plated in a medium containing 6-thioguanine.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 60 Hz
Exposure duration: 12 h

General information

Prior to the MF exposure samples were treated with 2 Gy at 1.76 Gy/min gamma radiation.

Exposure 1

Main characteristics
Frequency 60 Hz
Type
Waveform
Exposure duration 12 h
Exposure setup
Exposure source
Setup two electrically coupled solenoid coils (length 0.25 m, diameter 0.13 m) were wound in 348 turns of magnetic wire on a cylindrical support
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
magnetic flux density 0.7 mT effective value measured - -
magnetic flux density 0.47 mT effective value measured - -
magnetic flux density 0.23 mT effective value measured - -
electric field strength 3 µV/cm maximum calculated - in the center of the cells
current density 0.05 µA/cm² maximum calculated - in the center of the cells

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

An increase in the hypoxanthine-guanine phosphoribosyl transferase gene mutation frequency induced by gamma rays was observed in magnetic field exposed cells. The increase was dependent on the applied magnetic flux density and enhanced with higher magnetic flux densities.
The magnetic field exposure did not enhance the gamma radiation-induced cytotoxicity.
These data indicate that moderate-strength, oscillating magnetic fields may act as an enhancer of mutagenesis in mammalian cells.

Study character:

Study funded by

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