The importance of the intramolecular disulfide bridges in porcine somatotropin for its biological activity.

The dependance of the porcine somatotropin activity on the entireness of the intrachain disulfide bridges is investigated in three biological systems: bioassay in vivo, radioimmuno assay and receptor assay with rat liver membranes. Cleavage of the disulfide bridges is accomplished by reduction, oxidation and sulfitolysis, respectively. In no case is the hormone activity completely abolished with regard to measurements in the bioassay and radioimmuno assay. In the radioligand assay with rat liver membranes neither native porcine somatotropin nor the treated hormone preparations are bound by the receptors.