Corticotropin-induced changes in protein labelling: lack of molecular specificity

Previous studies in this and other laboratories have indicated that corticotropin (ACTH) administered to intact or hypophysectomized rats or mice increased the labelling of cerebral proteins by radioactive amino acids, presumably indicative of increased protein synthesis. This study was designed to reveal whether this increased labelling was specific for particular proteins by studying labelling patterns in SDS polyacrylamide gels using a double isotope procedure. Two strains of mice, two different amino acid precursors, leucine and lysine, and both peripheral and central administration of ACTH and amino acids were used. In no case were treatment dependent changes in labelling observed in any region of the gel. This included regions containing S-100 or NSP, two brain specific proteins whose content had been reported to be increased by treatment of rats with an ACTH analog.