Effect of Low Potassium Diet on Rat Exercise Hyperthermia and Heatstroke Mortality.

摘要

A total of 182 male Sprague-Dawley rats weighting between 250-300 g were fed either a control (n=60) or low-potassium (n=122) diet for 32 days. The diets contained either 125 or 8 mEq potassium per kg, respectively. Rats fed the low k+ diet gained weight at only one third the rate of controls (1.7 vs 5.2 g/d) and their skeletal muscle and plasma potassium levels were reduced by 28 and 47%, respectively. When run to exhaustion at either 15 or 20 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 kg M of work than controls (0.12 vs 0.05 C). However, there were no differences in susceptibility to heatstroke mortality (LD50 = 41.3 + or - 0.1 C for both groups). Post-exercise increases in circulating potassium (>90%) of heat-injured rats raised the plasma levels of low K+ fed rats to normal (5.9 + or - 2.2 mEq/L). Heart lesions (90% incidence) but not kidney lesions were induced by low K+ feeding. Control rats exercised to exhaustion exhibited clinical and histological evidence of a hierarchy of tissue injury (liver>heart>skeletal muscle) consistent with exertion-induced heatstroke. (Author)