Study type: Medical/biological study (experimental study)

Microwave-induced increase of water and conductivity in submaxillary salivary gland of rats. med./bio.

Published in: Bioelectromagnetics 1981; 2 (1): 51-60

Aim of study (acc. to author)

Hypersalivation is an important mechanism for heat dissipation by animals without sweat glands during hyperthermia. The water content and conductivity in submaxillary salivary glands and in other tissues were examined in rats exposed to microwaves or to conventional heat at 40°C.

Endpoint

Exposure

Exposure Parameters
Exposure 1: 2.88 GHz
Modulation type: pulsed
Exposure duration: 30 min
Exposure 2: 2.88 GHz
Modulation type: pulsed
Exposure duration: 15 min
  • power density: 420 W/m² unspecified (9.5 W/kg corresponding SAR (calculated))
Exposure 3: 2.88 GHz
Modulation type: pulsed
Exposure duration: 30 min
  • power density: 420 W/m² unspecified (9.5 W/kg corresponding SAR (calculated))
Exposure 4: 2.88 GHz
Modulation type: pulsed
Exposure duration: 60 min
  • power density: 420 W/m² unspecified (9.5 W/kg corresponding SAR (calculated))

Exposure 1

Main characteristics
Frequency 2.88 GHz
Exposure duration 30 min
Additional info 80 rats were exposed individually to microwaves and 50 were sham exposed
Modulation
Modulation type pulsed
Pulse width 1.5 µs
Repetition frequency 1,000 Hz
Exposure setup
Exposure source
  • 17 dB pyramidal antenna 30 cm x 30 cm aperture
Chamber Anechoic chamber (Faraday cage on the exterior)/ 3 m x 2 m x 2 m
Setup rats were placed one at a time in a Styrofoam box / 25 cm x 23 cm x 20 cm situated below the antenna
Additional info The applied microwave power was controlled either by adjusting the current to the magnetron or by changing the distance between cage and the antenna between 22 and 40 cm.
Parameters
Measurand Value Type Method Mass Remarks
power density 285 W/m² unspecified measured - 6.3 W/kg corresponding SAR (calculated)
power density 190 W/m² unspecified measured - 4.2 W/kg corresponding SAR (calculated)
power density 305 W/m² unspecified measured - 6.8 W/kg corresponding SAR (calculated)
power density 380 W/m² unspecified measured - 8.4 W/kg corresponding SAR (calculated)
power density 420 W/m² unspecified measured - 9.5 W/kg corresponding SAR (calculated)
power density 500 W/m² unspecified measured - 10.8 W/kg corresponding SAR (calculated)
power density 600 W/m² unspecified measured - 12.6 W/kg corresponding SAR (calculated)

Exposure 2

Main characteristics
Frequency 2.88 GHz
Exposure duration 15 min
Additional info 33 rats were exposed individually to microwaves, 32 were used for control and 10 were sham exposed
Modulation
Modulation type pulsed
Pulse width 1.5 µs
Repetition frequency 1,000 Hz
Exposure setup
Exposure source
Distance between exposed object and exposure source 0.4 m
Additional info The control rats were exposed one at a time for similar periods to heat (40°C).
Parameters
Measurand Value Type Method Mass Remarks
power density 420 W/m² unspecified measured - 9.5 W/kg corresponding SAR (calculated)

Exposure 3

Main characteristics
Frequency 2.88 GHz
Exposure duration 30 min
Additional info 33 rats were exposed individually to microwaves, 32 were used for control and 10 were sham exposed
Modulation
Modulation type pulsed
Pulse width 1.5 µs
Repetition frequency 1,000 Hz
Exposure setup
Exposure source
Distance between exposed object and exposure source 0.4 m
Additional info The control rats were exposed one at a time for similar periods to heat (40°C).
Parameters
Measurand Value Type Method Mass Remarks
power density 420 W/m² unspecified measured - 9.5 W/kg corresponding SAR (calculated)

Exposure 4

Main characteristics
Frequency 2.88 GHz
Exposure duration 60 min
Additional info 33 rats were exposed individually to microwaves, 32 were used for control and 10 were sham exposed
Modulation
Modulation type pulsed
Pulse width 1.5 µs
Repetition frequency 1,000 Hz
Exposure setup
Exposure source
Distance between exposed object and exposure source 0.4 m
Additional info The control rats were exposed one at a time for similar periods to heat (40°C).
Parameters
Measurand Value Type Method Mass Remarks
power density 420 W/m² unspecified measured - 9.5 W/kg corresponding SAR (calculated)

Exposed system:

Methods Endpoint/measurement parameters/methodology

Investigated system:
Investigated organ system:
Time of investigation:
  • after exposure

Main outcome of study (acc. to author)

1) In animals exposed to microwaves colonic temperature was elevated significantly at a SAR of 4.2 W/kg, while water content and conductivity in submaxillary salivary gland increased significantly at SAR values of 6.3 W/kg and higher.
2) Higher colonic temperatures and greater increase in the water content of submaxillary salivary gland were revealed in animals after 15 or 30 min exposures to microwaves at a SAR of 9.5 W/kg than were found in animals exposed to heat at 40°C. Also, submaxillary salivary gland conductivity was significantly depressed by heat and significantly increased by microwaves after irradiation for 15 or 30 min.
3) The data support the hypothesis that water content and conductivity of submaxillary salivary gland of rats can be used as a sensitive specific test of a microwave induced thermal response.

Study character:

Study funded by