ACTH, corticosterone, and beta-endorphin in rat blood plasma after prolonged immobilization stress

To assess functional relations between changes in ACTH, beta-endorphin (BE), and corticosterone (CS) levels, plasma concentrations of these hormones were studied in rats during the development of prolonged immobilization stress. Plasma hormone concentrations were determined by radioimmunoassay. The results were analyzed by standard statistical methods on a microcomputer. A particular feature about the kit used to determine BE was the presence of 50% cross-reactivity of the antiserum against beta-lipotrophin. To determine CS a highly specific antiserum produced by a laboratory was used