State of creatine in mammalian heart muscle

¹ Department of Physiology, Medical School, University of Minnesota, Minneapolis, Minnesota

Studies were performed on the total creatine, phosphocreatine and inorganic phosphate content of rabbit ventricular muscle from animals sacrificed under various conditions. The highest values of phosphocreatine, averaging 59.6% of the total creatine, were found in hearts arrested by intra-aortic infusion of alkaline potassium citrate solutions. Approximately the same values were found after sodium citrate arrest. Potassium chloride arrest resulted in a finding of only half as much phosphocreatine. Hearts removed without previous arrest likewise showed phosphocreatine values far below those found after citrate arrest. Acetylcholine arrest did not yield high values. Animals sacrificed by stunning, followed immediately by artificial respiration with 100% O₂ showed the lowest quantities of cardiac phosphocreatine. Adrenaline administration to the animal prior to potassium citrate arrest was followed by very low phosphocreatine levels. The inorganic phosphate content of rabbit heart muscle is in general inversely proportional to the phosphocreatine, and directly proportional to the free creatine levels. Assuming a linear correlation one finds that there appears to be 75 mg% of free creatine in the rabbit ventricular muscle at the time of instantaneous arrest under optimal conditions.