Journal of Applied Physiology, Vol 52, Issue 4 1049-1058, Copyright © 1982 by American Physiological Society
Adjustments in metabolic heat production by squirrel monkeys exposed to microwaves
E. R. Adair and B. W. Adams
Squirrel monkeys (Saimiri sciureus) were exposed in the far field of a horn
antenna to both brief (10-min) and prolonged (90-min) periods of 2,450-MHz
continuous microwaves. Ambient temperature (Ta) was constant at 15, 20, or
25 degrees C. Microwave power density ranged from 2.5 to 10 mW/cm2,
representing a range of whole-body energy absorption from 0.4 to 1.5 W/kg.
Reliable reductions in metabolic heat production (M), calculated from
oxygen deficit in the monkey's expired air, were initiated at all Ta by
10-min whole-body exposures to power densities of 4 mW/cm2 (2 monkeys) or 6
mW/cm2 (1 monkey) and above. The magnitude of M reduction was linearly
related to microwave intensity above the threshold level. Termination of
microwaves was followed by a rapid M rebound. The change in M produced by a
given power density was nearly the same in Ta = 15 and 20 degrees C. During
90-min exposures at Ta = 20 degrees C, the vigorous M reduction to
microwave onset adapted slowly, ensuring continual precise regulation of
internal body temperature. Thus cold-exposed endotherms readily compensate
for microwave-induced body heating by reducing endogenous heat production.
