[The development of theories on the mechanisms of insulin action]

In 1924 Laufberger formulated his block theory on the action of insulin. Its basic thesis that insulin prevents the new formation of glucose and its supply into the blood stream is still valid, although knowledge on the multiple action of insulin expanded substantially. The theory put forward in 1955 by Levine and Goldstein which ascribed all insulin actions to the influence on the cellular membrane permeability for glucose, could, however, not explain all data associated with insulin, the knowledge of which was expanded steadily. At present the mechanism of insulin action is explained most comprehensively by the concept based on the bond of insulin to its membrane receptor which by activation of tyrosine kinase it contains induces either cascade phosphorylation of intracellular protein kinases or (and) leads to the release of the "second messenger" from the cell membrane, i.e. of glycosyl-phosphatidyl inositol. In both instances activation of the glucose and amino acids transmitter from the medium into the cells results, as well as activation of enzymes catalyzing in the cell various degrees of carbohydrate, fat and protein metabolism.