ABSTRACT
Many of Claude Bernard's pioneering observations, made 128 years ago regarding fundamental principles of glycogen metabolism in the mammal, are still valid today.' However, it has since been established that the synthesis and breakdown of glycogen is a highly complex and tightly controlled process involving substrates, intermediates, cofactors, activators, inhibitors, enzymic interconversions, and hormonal balances. Glycogen metabolism occurs in many tissues, however, these various controls are different in each tissue and are adapted to the particular environment and metabolic requirements of each organ. For example, regulation of glycogen synthesis and breakdown in the mammalian liver differs markedly from its regulation in muscle, each one serving a different function; whereas glycogenolysis in the liver leads primarily to the liberation of glucose into the blood, glycogenolysis in the muscle provides energy for vigorous muscle contraction.
