• Reginald Matejec, Heinz-W Harbach, Rolf-H Bödeker, Gunter Hempelmann, and Hansjörg Teschemacher.
• Department of Anaesthesiology, Intensive Care Medicine and Pain Therapy, Justus-Liebig-University, Giessen, Germany. reginald.matejec@chiru.med.uni-giessen.de
• Clin J Pain. 2006 Feb 1; 22 (2): 113-21.

BackgroundIn the pituitary of lower species, pro-opiomelanocortin is expressed in corticotroph cells of the anterior and in melanotroph cells of the neurointermediate lobe; enzymatic processing in the corticotrophs results in the release of adrenocorticotropic hormone, beta-lipotropin, or beta-endorphin. In the melanotrophs, these fragments are further modified, eg, by N-terminal acetylation. In the human pituitary, these enzyme systems are located within the same cells in the anterior lobe. We studied the reactions of the pro-opiomelanocortin system under preoperative conditions as well as under postoperative pain.MethodsIn 17 patients undergoing hip or knee arthroplasty, we determined plasma concentrations of N-acetyl-beta-endorphin immunoreactive material, authentic beta-endorphin [beta-endorphin(1-31)], adrenocorticotropic hormone, beta-lipotropin immunoreactive material, and cortisol, as well as pain severity rated by the patients using a visual analogue scale before surgery, after surgery but still under spinal anesthesia, under postoperative pain, and 1 day after surgery.ResultsOnly low levels of N-acetyl-beta-endorphin immunoreactive material were measured in 16 out of 17 patients. High concentrations (1st quartile/median/3rd quartile; pmol/L) of adrenocorticotropic hormone (22.5/55.8/124) and beta-lipotropin immunoreactive material (6.6/34.6/142) were observed under postoperative pain, accompanied by a small increase of beta-endorphin(1-31) concentrations (0.0/6.1/10.9). Preoperatively small but significantly elevated levels of corticotroph-type and melanotroph-type pro-opiomelanocortin derivatives were observed; in contrast, spinal anesthesia suppressed all pro-opiomelanocortin fragment release. Postoperative pain severity correlated with postoperative adrenocorticotropic hormone, beta-lipotropin immunoreactive material, and beta-endorphin(1-31) concentrations.ConclusionsWe conclude that the melanotroph-type pro-opiomelanocortin system is not activated under postoperative pain; the increase of corticotroph-type pro-opiomelanocortin fragment levels is different in quantity and proportion under preoperative conditions or postoperative pain, respectively.

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