Variations in Muscle Electrolyte Composition Due to Sampling and to Aging.

Abstract

Variation in muscle electrolyte composition was tested by taking samples from the thigh and from the paravertebral muscles of 2 groups of normal rats aged 11 and 18 weeks respectively. The thigh muscle in each instance contained more chloride and less K than the back muscles when the data were expressed in terms of day fat-free solids. The difference in K was not observed when it was expressed as concentration in calculated intra-cellular water. It was postulated that the differences noted were due to differences in the connective tissue content of the 2 samples. A decrease in muscle K concentration with increasing age (11-18 weeks) was observed. It was noted that a reciprocal increase in muscle Na concentration occurred so that the sum of the 2 remained constant.