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β-endorphin (1-31) in the plasma of male volunteers undergoing physical exercise

2000; Elsevier BV; Volume: 25; Issue: 6 Linguagem: Inglês

10.1016/s0306-4530(00)00009-3

1873-3360

Heinz W. Harbach, Kornelia Hell, Christian Gramsch, Norbert Katz, G. Hempelmann, Hansjörg Teschemacher,

Neuropeptides and Animal Physiology

beta-Endorphin is an opioid peptide representing the C-terminal 31 amino acid residue fragment of proopiomelanocortin (POMC). The release of beta-endorphin from the pituitary into the cardiovascular compartment under physical or emotional stress has been frequently reported. However, besides beta-endorphin (1-31), nine acetylated or non-acetylated beta-endorphin analogues exist - in addition to N-terminally elongated beta-endorphin derivatives such as beta-lipotropin (beta-LPH). Since conventional radioimmunoassays (RIAs) and even commercially available two site-RIAs pick up at least some of those beta-endorphin derivatives, only "beta-endorphin immunoreactive materials" and not authentic beta-endorphin have been determined in those studies. We have developed a highly specific two site-RIA for beta-endorphin (1-31), which does not cross-react with all beta-endorphin derivatives known to occur as yet. Using this RIA as well as further assays for determination of beta-endorphin (1-31), beta-endorphin immunoreactive material (IRM), ACTH and Cortisol in the plasma of 14 volunteers upon intensive physical exercise, we found authentic beta-endorphin only in about 50% of the plasma samples, representing therein only a minor portion of the beta-endorphin IRM.