Influence of Amino Acids and of Protein Diet Upon Creatine Content of the Myocardium

Abstract

Beard and Barnes 1 have reported that the feeding of various amino acids and proteins resulted in an increase in the creatine (total creatinine) concentration in skeletal muscle tissue. Preparatory to a study of the influence of dietary ingredients upon the reduction in the creatine content of heart muscle, produced by experimental thyrotoxicosis 2 and other procedures, the influence of feeding various amino acids and of the protein intake upon the creatine content of the myocardium was observed.

Adult rats were fed the special diets for a period of 2 weeks. The 3 casein diets all contained 4% of the Osborne and Mendel salt mixture, 10% of brewers yeast, 10% cod liver oil and 15% lard. In order, they contained 6, 20 and 55% of casein, and 55, 41 and 6% respectively of cornstarch. The 20% casein diet served as the control diet and for the addition of amino acids. Muscle creatine was determined by the method of Rose, Helmer and Chanutin. 3

Table I shows that the higher the protein content of the diet the lower the concentration of creatine in the myocardium. This is surprising and may be due to the variable carbohydrate intake, a point which is being examined. The addition of glycine or dl-alanine to the diet definitely raised the amount of creatine in the heart muscle, d-glutamic acid was not so effective. The relative effects of the various amino acids, particularly over short periods of time in the same manner as used by Beard and Barnes 1 for skeletal muscle, should be determined.