Effect of Ischemia on Adenine Nucleotides in Cardiac and Skeletal Muscle

Rabbit skeletal muscle contains 56% more ATP and 225% more creatine phosphate than rabbit cardiac muscle. With ischemia the per cent reduction in ATP and creatine phosphate is less in skeletal than cardiac muscle and ADP and AMP decrease in skeletal and increase in cardiac muscle, IMP is present in skeletal muscle and increases with ischemia, whereas it is absent in cardiac muscle but appears with ischemia. Adenosine, inosine, and hypoxanthine are absent in skeletal and cardiac muscle. Ischemia results in the appearance of adenosine, inosine, and hypoxanthine in cardiac muscle but only the latter two compounds appear in ischemic skeletal muscle. Although complete ischemia is required to demonstrate the presence of adenosine in cardiac muscle, the appearance of this nucleoside is nevertheless consistent with the hypothesis that under physiological conditions quantities of adenosine, undetectable by present methods, may play a role in the regulation of coronary blood flow.