Journal of Applied Physiology, Vol 38, Issue 4 630-635, Copyright © 1975 by American Physiological Society
Thermoregulatory, metabolic, and cardiovascular response of rats to microwaves
R. D. Phillips, E. L. Hunt, R. D. Castro and N. W. King
This study was undertaken to determine the effects of 2,450-MHz microwave
irradiation on thermoregulation, metabolism, and cardiovascular function of
rats. Young adult male animals (430 g) were exposed for 30 min to 2,450-MHz
microwaves in a cavity at absorbed dose rates of 0, 4.5, 6.5, or 11.1 mW/G.
For animals of the size used in this study, these dose rates represent
absorption of energy at the rate of 27.7, 40.1, and 68.2 cal/min,
respectively. For a period of 5 h following exposure, measurements were
made of colonic temperature, skin temperature, oxygen consumption, carbon
dioxide production, respiratory quotient, and heart rate. Rats that
received 27.7 cal/min for 30 min exhibited an initial transient increase in
colonic and skin temperatures but no alterations in other functions. The
group irradiated at 40.1 cal/min had greater elevations in colonic and skin
temperatures immediately after exposure, followed by overcompensation and
lower than normal colonic temperatures for about 3 h. The metabolic rate
was depressed in this group for 3 h. Bradycardia developed within 20 min
after exposure and persisted for about 3 h. The group of rats that received
68.2 cal/min for 30 min had responses similar to those of the 40.1 cal/min
group, but the changes were more severe and lasted longer. In addition, a
number of transient abnormalities were noted in the ECG tracings of rats
that had received the highest dose, including irregular rhythms and
incomplete heart block. The physiological changes observed in this study
can be attributed to the heating induced by irradiation.
