Study type: Medical/biological study (experimental study)

Increased ornithine decarboxylase activity in cultured cells exposed to low energy modulated microwave fields and phorbol ester tumor promoters. med./bio.

Published in: Cancer Res 1988; 48 (15): 4222-4226

Aim of study (acc. to editor)

To study the ornithine decarboxylase activity in cultured cells exposed to low energy modulated microwave fields and phorbol ester tumor promotors.

Background/further details

Ornithine decarboxylase activity is regulated by a wide variety of growth factors and hormones active on the cell surface. Cyclic AMP and phorbol ester tumor promotors, in addition to other membrane-active compounds, have been shown to rapidly modulate ornithine decarboxylase activity. The tumor-promoting phorbol esters, including TPA used in this study, have a specific membrane receptor, the calcium-phospholipid kinase (protein kinase C). Since latent cell transformation manifested in the presence of phorbol esters has been reported following low-level microwave exposure, ornithine decarboxylase might be a sensitive molecular marker of field-related actions related to the process of tumor promotion.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 450 MHz
Modulation type: AM
Exposure duration: continuous for 1 h
Exposure 2: 450 MHz
Modulation type: AM
Exposure duration: continuous for 1 h

Exposure 1

Main characteristics
Frequency 450 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 1 h
Modulation
Modulation type AM
Modulation frequency 16 Hz
Modulation depth 85 %
Additional info

sinusoidally modulated at 75-85%

Exposure setup
Exposure source
Chamber The long axis of the Crawford cell was oriented vertically inside a large incubator at 37 ± 0.5°C.
Setup Cell cultures of 10 ml in circular Petri dishes (75 cm²) were placed in a gas-tight Lucite box inside the Crawford cell near the center of the long axis at a distance of 1 cm from each other. Air containing 5% CO2 at 100% humidity was passed continuously into the Lucite culture chambers.
Sham exposure A sham exposure was conducted.
Additional info Control cultures were placed in the same incubator in a similar box outside the Crawford cell.
Parameters
Measurand Value Type Method Mass Remarks
power 1.7 W peak value measured - -
power density 1 mW/cm² peak value measured - -

Exposure 2

Main characteristics
Frequency 450 MHz
Type
Charakteristic
  • guided field
Exposure duration continuous for 1 h
Modulation
Modulation type AM
Modulation frequency 100 Hz
Modulation depth 85 %
Additional info

sinusoidally modulated at 5, 10, 16, 20, 60, and 100 Hz

Exposure setup
Exposure source
Sham exposure A sham exposure was conducted.
Parameters
Measurand Value Type Method Mass Remarks
power 1.7 W peak value measured - -
power density 1 mW/cm² peak value measured - -

Reference articles

  • Adey WR et al. (1982): Effects of weak amplitude-modulated microwave fields on calcium efflux from awake cat cerebral cortex.

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

In all three cell types, a 1-h radiation produced a significant (up to 50%) increase in ornithine decarboxylase activity in comparison to the unexposed cultures. Following removal from the field, ornithine decarboxylase activity remained elevated in the exposed cells for more than a 3-h period in the Reuber H35 and CHO cells (the increase in the 294T cells persisted for only 1 h).
Modulation frequencies of 60 and 100 Hz failed to cause any alteration in ornithine decarboxylase activity in Reuber H35 cells following a 1-h radiation, in contrast to the 50% increase in enzyme activity brought about the 16 Hz modulated field.
The stimulated ornithine decarboxylase activity in the cultured cells that followed treatment with a phorbol ester tumor promotor (TPA) was potentiated by prior exposure to the same low energy electromagnetic field.The field did not alter either basal or TPA-stimulated DNA synthesis.

Study character:

Study funded by

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