Effect of low-potassium diet on rat exercise hyperthermia and heatstroke mortality.
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.
D000818:Animals; D001831:Body Temperature; D001835:Body Weight; D004032:Diet; D005334:Fever / Q000209:etiology*; D006359:Heat Exhaustion / Q000401:mortality*; D008297:Male; D009132:Muscles / Q000032:analysis; D005082:Physical Exertion; D011188:Potassium / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D012420:Running; D013997:Time Factors
D011188:Potassium