Vol. 288, Issue 2, 766-773, February 1999

Trauma Decreases Leucine Enkephalin Hydrolysis in Human Plasma

Reto Babst, Lucilla Bongiorno, Mario Marini, L. Giorgio Roda, Giulio Spagnoli and Alessandra Urbani

Research Division, Department of Surgery, University of Basel, Basel, Switzerland (R.B., G.S.); Dipartimento di Medicina Sperimentale, Università degli Studi "Tor Vergata," Rome, Italy (L.B.); and Dipartimento di Neuroscienze, Università degli Studi "Tor Vergata," Rome, Italy (M.M., L.G.R., A.U.)

Plasma hydrolysis of leucine enkephalin was evaluated, together with several cellular immune parameters, in a homogeneous group of human subjects who had undergone severe trauma (proximal femur fracture); data obtained were compared with those obtained in an age-matched control group. In the experimental group, immediately after hospitalization, substrate hydrolysis was reduced with respect both to the control subjects and the same patients 4 weeks after the trauma. Chromatographic separation of the enzymes active on leu-enkephalin showed that the reduction of substrate hydrolysis is mainly attributable to the decrease in the activity of enkephalin-degrading enzymes, principally of aminopeptidases, per se, whereas the role of the low-molecular-weight plasma inhibitors is only minor. In the same subjects, several of the immunological parameters measured underwent modifications that may be considered stress related. However, the absence of a quantitative relationship between reduction in hydrolysis and modifications of immune parameters does not support the hypothesis of a direct relationship between these two sets of data.