Attenuation of neutrophil and endothelial activation by intravenous morphine in patients with acute myocardial infarction

To investigate the effects of morphine on neutrophil and endothelial activation, we measured serum levels of intercellular adhesion molecule-1 (ICAM-1), L-selectin, and neutrophil endopeptidase 24.11 (NEP) in 38 patients with acute myocardial infarction (group 1) and 16 control subjects (group 2). In group 1, all the patients underwent blood sampling at initial presentation and 10 minutes later. Twenty of them had 3 mg of morphine administered intravenously immediately after the first sampling (group 1A) and the other 18 after a second sampling (group lB). The serum levels of ICAM-1 and L- selectin were both significantly higher in groups 1A and 1B than in group 2. In group 1A, the ICAM-1 decreased significantly at second blood samplings (310 ± 28 vs 368 ± 30 ng/ml; p <0.001), whereas in group lB there was no significant change in ICAM-1 (357 ± 33 vs 359 ± 26 ng/ml; p = NS). In group 1A, the L-selectin decreased significantly at second blood samplings (2.3 ± 1.2 rag/L, p <0.001 vs baseline), whereas in group lB there was no significant change in L-selectin (3.9 ± 1.0 mg/L, p = NS vs baseline). There was no significant difference in baseline NEP activities between groups 1A and 1B (4.89 ± 1.22 vs 5.14 ± 1.57 nmol/mg protein; p = NS). However, the NEP activities at second blood samplings decreased significantly in group 1A (9.88 ± 1.86 nmol/mg protein, p <0.001 vs baseline), whereas no significant changes were observed in group lB (5.09 ± 1.62 nmol/mg protein, p = NS vs baseline). In conclusion, morphine increased NEP activities and thus attenuated shedding of L-selectin and ICAM-1.