IBUPROFEN PROTECTS RAT LIVERS FROM OXYGEN-DERIVED FREE RADICAL-MEDIATED INJURY AFTER TOURNIQUET SHOCK

Rats subjected to tourniquet shock suffer a severe form of circulatory shock, tissue and organ oxidative stress, and final multiple system o rgan failure (MSOF) and death of the animals within 24 h of tourniquet release. The oxidative damage observed in hind-limb muscle tissue aft er reperfusion does not by itself account for the final systemic and l ethal MSOF. We have postulated that organ failure has its genesis in a primary perfusion abnormality, e.g. the hind limbs, which is followed by secondary hypoperfusion of other organs, such as the liver, as has been shown to be the case in several septic shock models. It has also been shown that injured or necrotic tissue can activate neutrophils, Kupffer cells, platelets, and both the complement and coagulation casc ades. In turn, complement activation also leads to neutrophil and Kupf fer cell activation as assessed by their capacity to generate oxyradic als. Herein we have evaluated the potential protective effect of ibupr ofen on hepatic oxygen-derived free radical production, as well as its effects on both polymorphonuclear leucocyte (PMN) activation and live r infiltration. The protective effect of ibuprofen on hepatic oxidativ e injury was assessed by determining total thiol groups (SH), thiobarb ituric acid-reactive substances (TEARS), and by the release of asparti c acid (AsT) and alanine (AlT) aminotransferases in control animals, i n animals subjected to 5 h of tourniquets, and in animals after 2 h of hind-limb reperfusion. Liver infiltration by PMNs was determined by h istology after staining with eosin-hematoxylin, and PMN activation by their capacity to reduce nitro blue tetrazolium (NET). Our results sho w that total hepatic thiol content decreased significantly, over and a bove the the normal circadian decrease in liver glutathione, after the 5 h tourniquet period (from 6.16+/-0.97 to 4.07+/-0.21 mu moles/g w.w ). The decrease in liver thiols in animals pretreated with ibuprofen w as not significantly different from that in control animals (from 5.76 +/-0.21 to 4.69+/-0.19 mu moles/g w.w), and could be accounted for by the circadian effect. A further significant decrease was observed in t he control (3.01+/-0.12 mu moles/g w.w), but not in the ibuprofen pret reated rats (4.65 +/- 0.16 mu moles/g w.w), after the 2 h reperfusion period. TEARS production remained essentially unchanged during the tou rniquet period in both the control and ibuprofen pretreated animals (a verage 260 nmoles/g w.w), but increased significantly after hind-limb reperfusion in the control animals (386.9+/-18.5 nmoles/g w.w), but no t in the ibuprofen treated rats (267.2+/-7.4 nmoles/g we.w). The prote ctive effect of ibuprofen was also evident in plasma aminotransferase levels (AsT and AlT) which increased 14 and 6-foId, respectively, duri ng the experimental period in the untreated rats, and only 6 and 3-fol d in the animals pre-treated with the drug. No significant differences were observed in PMN liver infiltration in any of the animals, nor at any of the different time periods under study. Nevertheless, our resu lts indicate that there is a 3-fold increase (over control values) in the number of circulating activated PMNs after hind-limb reperfusion i n the non-protected control rats, and only a 2-fold increase in those protected by ibuprofen. It is concluded that ibuprofen: a) protects ra t livers from the oxidative stress which results after 2 h of reperfus ion of rat hind limbs subjected to 5 h of ischemia by means of tourniq uets, and b) significantly decreases the number of NET-positive PMNs i n the systemic circulation after hind-limb reperfusion.