Effects of Prolonged Administration of Moderate Doses of Creatine in Rats

Abstract

Since there were no observations reported in the literature on the long continued administration of creatine to experimental animals, it seemed worth while to conduct a series of observations on young and old animals in which creatine was fed in doses comparable to those used in certain clinical therapeutic experiments in man. This seemed especially desirable since unfavorable effects of long-time administration might conceivably occur. The series of experiments was further used in order to determine the influence of moderately high ingestion rates of creatine on the amount of that substance stored in various tissues in the body, particularly in muscle. Rats were, therefore, fed on the following stock diet, half of the animals receiving this diet alone, and the other half receiving the same food mixture with 2 gm. of creatine hydrate added to each kg. of food. Assuming an average food intake of 14 gm. per day per rat of 350 gm. weight, the creatine intake was 75 mg. creatine hydrate per kg. per day.

The rats were from 2 sources. One group consisted of 25 animals∗ age 3 years or over at the beginning of the experiment, which had been obtained from the breeding colony of the Wistar Institute. The other group was of 50 Wistar strain animals 15 months of age at the beginning of the experiment. One-half of the animals in each group were placed on the control and the experimental diets for a period of from 4–6 months, at which time those still living were sacrificed and analyses made. The animals were anesthetized with amytal, 50 mg. per kilo, intraperitoneally. The tissues analyzed were the gastrocnemius muscle, the liver, and heart, which were excised in that order and plunged immediately into liquid air on excision.