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.
Exposure duration: 12 h
|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|
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.