Journal of Applied Physiology, Vol 51, Issue 1 8-13, Copyright © 1981 by American Physiological Society
Effect of low-potassium diet on rat exercise hyperthermia and heatstroke mortality
R. W. Hubbard, M. Mager, W. D. Bowers, I. Leav, G. Angoff, W. T. Matthew and I. V. Sils
A total of 182 male Sprague-Dawley rats weighing 250-300 g were fed either
a control (n = 122) diet for 32 days. The diets contained either 125 or 8
meq potassium/kg, respectively. Rats fed the low-K diet gained weight at
only one-third the rate of controls (1.7 vs. 5.2 g/day), and their skeletal
muscle and plasma potassium levels were reduced by 28 and 47%,
respectively. When run to exhaustion at either 15 or 20 degrees C, low
K+-fed rats accomplished less than one-half of the work done by the
controls (26 vs. 53 kg. m) but exhibited a markedly greater rate of heat
gain per kilogram-meter of work than controls (0.12 vs. 0.05 degrees
C)ambient temperature of 20 degrees C, the rats of the low-K+ group despite
large differences in body weight (-25%), run time temperature and twice (33
vs 17%) the mortality rate of the controls. Postexercise increases in
circulating potassium (less than 90%) of heat-injured rats raised the
plasma levels of low K+-fed rats to normal (5.9 +/- 2.2 meq/l). These
results appear to characterize the existence of an insidious and,
therefore, undocumented form of fatal exertion-induced heat illness.
