The creatine content of muscle during starvation and its relation to urinary creatine

Abstract

There has recently arisen some little discussion with regard to the creatine concentration of muscle during starvation. Data have been submitted to show that inanition in the rabbit results in an increase in the content of muscle creatine, and it has further been argued that there is an actual increase in creatine formation. In other quarters, it has been claimed that starvation (experiments with the dog) produces a marked decrease in the percentage content of muscle creatine.

From nine experiments which we have already completed on starving rabbits, we can agree with both of these observations as regards an increase or a decrease in the content of the muscle creatine. In three experiments, a decided increase in the content of creatine in muscle has been found; in one the per cent. of creatine was normal, while in five it was even more strikingly below normal. In addition to the increased or normal creatine content of muscle, the first four animals mentioned showed an increased percentage content of creatine in the body. This we are not inclined to ascribe to an increased creatine formation.

The reason for this increased or decreased content of body and muscle creatine appears to be satisfactorily explained by our results. The animals having an increase in the content of muscle creatine eliminate a comparatively small amount of creatine in the urine, while those in which the muscle and total body creatine has been considerably depleted, eliminate an equally large amount of creatine in the urine. In other words, the content of muscle creatine during starvation is dependent upon the amount of and the rate of creatine excretion in the urine. Just why some animals eliminate creatine more rapidly than others, we are as yet unable to explain, although we assume that this is connected with the length of the fast and the state of nutrition of the animal.