To address the question of whether the increased plasma concentration of interleukin 6 (IL‐6) following strenuous muscular work could be related to exercise‐induced muscle damage, 5 moderately active male volunteers underwent two isokinetic exercise sessions in the eccentric mode, separated by a period of 3 weeks during which the subjects underwent five training sessions. Before training, exercise was followed by severe muscle pain (delayed‐onset muscle soreness; DOMS), and by significant increases in plasma IL‐6 level and serum myoglobin concentration (SMb) (P < 0.001). After training, postexercise DOMS and SMb values were significantly lower than those measured before training. There was no significant difference between plasma IL‐6 levels measured at the same time points before and after training. We conclude that the hypothetical relationship between exercise‐induced muscle damage and increased postexercise levels of circulating IL‐6 is not substantiated by the present results. © 1999 John Wiley & Sons, Inc. Muscle Nerve 22: 208–212, 1999

To examine whether endotoxaemia accompanying long-term, strenuous physical exercise is involved in exercise-induced increase in plasma tumour necrosis factor alpha (TNF-alpha) concentration and polymorphonuclear neutrophil (PMN) activation, 14 male recreational athletes [mean age 28 (SEM 1) years] were studied. Exercise consisted of a 1.5-km river swim, a 40-km bicycle race, and a 10-km road race. Mean time to complete the race was 149.8 (SEM 4.8) min. The plasma concentrations of granulocyte myeloperoxidase (MPO) and TNF-alpha were significantly higher than baseline values immediately and 1 h after exercise (P<0.001). Both variables returned to pre-race levels the day after exercise. Marked, transient decreases in plasma concentrations of anti-lipopolysaccharide (LPS) immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies directed against a panel of selected smooth gram-negative LPS were observed after the race, reaching in most cases minimal values in the blood sample drawn immediately following the completion of the triathlon. There was no significant correlation between the magnitude of PMN activation, as assessed by the increase in plasma concentrations of MPO, and the humoral markers of endotoxaemia and TNF-alpha. An inverse, highly significant relationship between the increase in plasma TNF-alpha concentrations and the changes in circulating anti-LPS IgM antibodies concentrations was observed (r = -0.7; P<0.01). These findings suggest that exercise-induced endotoxaemia was involved in the release of TNF-alpha, that the magnitude of the TNF-alpha response to exercise was down-regulated by anti-LPS antibodies of the IgM class, and that the production of TNF-alpha and endotoxaemia did not seem to play a role in the activation of circulating PMN in the exercising subjects.

The role of angiotensin-converting enzyme (ACE) in the metabolism of bradykinin (BK) has been studied in several tissues. However, and contrary to angiotensin I, the metabolism of BK at the cardiac level has not been investigated. In this study, we define the participation of ACE in the carboxy-terminal degradation of BK in heart membranes of the dog, human, rabbit, and rat. The calculation of the kinetic parameters characterizing the metabolism of BK and the generated des-Arg9-BK can be summarized as follows: the half-life ( t 1/2) of BK [dog (218 ± 32 s) > human (143 ± 9 s) = rat (150 ± 4 s) > rabbit (22 ± 2 s)] and of des-Arg9-BK [dog (1,042 ± 40 s) > human (891 ± 87 s) > rat (621 ± 65 s) > rabbit (89 ± 8 s)] both showed significant differences according to species. Enalaprilat, an ACE inhibitor, significantly prevented the rapid degradation of BK and des-Arg9-BK in all species studied, whereas retrothiorphan, a neutral endopeptidase inhibitor, and losartan, an angiotensin II type I receptor antagonist, did not affect this metabolism. The relative importance of ACE in the cardiac metabolism of BK was species related: dog (68.4 ± 3.2%) = human (72.2 ± 2.0%) > rabbit (47.7 ± 5.0%) = rat (45.3 ± 3.9%). ACE participation in the metabolism of des-Arg9-BK was as follows: rabbit (57.0 ± 4.0%) > dog (39.9 ± 8.8%) = human (25.4 ± 5.5%) = rat (36.0 ± 7.0%). The participation of cardiac kininase I (carboxypeptidase M) in the transformation of BK into des-Arg9-BK was minor: human (2.6 ± 0.1%) > dog (0.9 ± 0.1%) = rabbit (1.0 ± 0.1%) = rat (1.0 ± 0.1%). These results demonstrate that ACE is the major BK-degrading enzyme in cardiac membranes. However, the metabolism of exogenous BK by heart membranes is species dependent. Our observations could explain some discrepancies regarding the contribution of kinins in the cardioprotective effects of ACE inhibitors.

Our study suggests that TAP block and intravenous lignocaine do not improve the post-operative analgesia provided by systematic administration of paracetamol after open prostatectomy.

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