title: Effects of glucocorticoids on peptide chain initiation in heart and skeletal muscle.
abstract: Treatment of rats for 5 days with cortisone acetate reduced synthesis of skeletal muscle protein by 56% compared to untreated controls, but had no effect on protein synthesis in heart. The reduction in synthesis in skeletal muscle was accounted for by both a loss of tissue RNA and development of a block in peptide-chain initiation. Activity of an eIF-2-like initiation factor decreased in psoas muscle of hormone-treated rats in proportion to the loss of RNA. Peptide-chain initiation, RNA content, and initiation factor activity were unaffected in heart muscle. In skeletal muscle of rats treated for 4 hr with dexamethasone, peptide-chain initiation was inhibited, whereas tissue RNA content and initiation factor activity were unchanged. These experiments suggested that total activity of eIF-2 did not always correlate with the rate of initiation, but that there did appear to be a relationship between initiation factor activity and tissue RNA content. Purification of eIF-2 from bovine heart muscle was undertaken in order to directly investigate the mechanism by which glucocorticoids modify eIF-2-activity and control peptide-chain initiation.
mesh_terms: D000818:Animals; D001835:Body Weight; D003348:Cortisone / Q000494:pharmacology*; D005938:Glucocorticoids; D009132:Muscles / Q000032:analysis / Q000033:anatomy & histology; D009206:Myocardium / Q000032:analysis*; D009929:Organ Size; D010442:Peptide Chain Initiation, Translational / Q000187:drug effects*; D010448:Peptide Initiation Factors / Q000302:isolation & purification / Q000494:pharmacology; D010649:Phenylalanine / Q000378:metabolism; D012313:RNA / Q000096:biosynthesis; D051381:Rats
chemical_list: D005938:Glucocorticoids; D010448:Peptide Initiation Factors; D010649:Phenylalanine; D012313:RNA; D003348:Cortisone