The mechanism of action of polypeptide hormones with special reference to insulin's action on glucose transport.

In the last decade substantial progress has been made in elucidation of the mechanisms of action of polypeptide hormones. For instance, it has become clear that these hormones bind to their target cells and that at least one component of the binding is saturable. This phenomenon, which is usually called receptor binding, is believed to be the first and necessary event in the chain of processes which lead to effects of the hormone on their target cells. Receptor binding is just one aspect of the mechanism of action of polypeptide hormones. The properties of binding differ from hormone to hormone as do the events after binding. The purpose of this communication is to describe some aspects of the mechanism of insulin action on transmembrane glucose transport, and to disucss general aspects of polypeptide hormone action in relation to the specific findings with insulin. Comprehensive reviews on polypeptide hormone receptors have been published recently (Freychet, 1976; Kahn, 1976).