Trauma decreases leucine enkephalin hydrolysis in human plasma

Plasma hydrolysis of leucine enkephatin was evaluated, together with severa l cellular immune parameters, in a homogeneous group of human subjects who had undergone severe trauma (proximal femur fracture); data obtained were c ompared with those obtained in an age-matched control group. In the experim ental group, immediately after hospitalization, substrate hydrolysis was re duced with respect both to the control subjects and the same patients 4 wee ks after the trauma. Chromatographic separation of the enzymes active on le uenkephalin showed that the reduction of substrate hydrolysis is mainly att ributable to the decrease in the activity of enkephalin-degrading enzymes, principally of aminopeptidases, per se, whereas the role of the low-molecul ar-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 relations hip between reduction in hydrolysis and modifications of immune parameters does not support the hypothesis of a direct relationship between these two sets of data.