EFFECTS OF CHRONIC DIETARY CREATINE FEEDING ON CARDIAC ENERGY-METABOLISM AND ON CREATINE CONTENT IN HEART, SKELETAL-MUSCLE, BRAIN, LIVER AND KIDNEY

Little is known about the regulation of total creatine concentration i n heart, skeletal muscle, brain, liver and kidney in response to incre ased dietary creatine intake. The phosphorylated fraction of intracell ular creatine (phosphocreatine) remain relatively constant, and theref ore, higher intracellular creatine levels may increase the energy rese rve of the heart [phosphocreatine and phosphoryl transfer via creatine kinase (CK)] and of other organs. To test the effect of supplying exo genous creatine on the myocardial energy reserve and on creatine conte nt of various organs, rats were given chow containing 0 (Untreated), 1 , 3, 5, or 7% (of diet weight) creatine for similar to 40 days. Therea fter, hearts were perfused and left Ventricular developed pressure and heart rate were recorded. High energy phosphate concentrations were d etermined with P-31-NMR spectroscopy, CK reaction velocity by P-31-mag netization transfer. Total creatine was determined in heart, skeletal muscle, brain, liver, kidney and serum by high-performance liquid chro matography (HPLC), Creatine feeding increased serum creatine by 73% (1 % creatine), 142% (3%), 166% (5%) and 202% (7%). In the heart, increas ed serum creatine levels did not affect mechanical function; ATP, phos phocreatine, inorganic phosphate, CK reaction velocity and total creat ine were all unchanged. Total creatine also remained constant in brain and skeletal muscle, while creatine content increased 4.6-fold in the liver and 1.9-fold in the kidney. We conclude that myocardial energy reserve via CK cannot be increased by exogenous creatine treatment. (C ) 1998 Academic Press Limited.