Biological Activity of Natural and Synthetic Insulin A-chain Preparations on the Isolated Rat Diaphragm

Abstract

THE possibility that separated insulin chains may be active to a certain extent on some of the insulin activity tests at present available has been repeatedly put to question within recent years either with insulin derivatives^1,2 or with other disulphide hormones³. Dixon and Wardlaw² demonstrated that, when all disulphide linkages of insulin were cleaved by sulphitolysis, none of the resulting thiosulphate derivatives of the A and B chains was active on glycogen deposition in the isolated mouse diaphragm or in the mouse convulsion test. If, however, the primary action of insulin on the receptor tissue is mediated by a disulphide–sulphydryl interchange, as suggested by the action of N-ethylmaleimide on the cell membrane^4–6, an at least partially intact disulphide structure would be required for this action.