Protective effects of aspirin in endotoxic shock.

Endotoxic shock is associated with increased metabolism of arachidonic acid to thromboxanes (TX) and prostaglandins (PG). This study assessed the effects of varied doses of aspirin, an inhibitor of arachidonic acid metabolism, on Salmonella enteriditis endotoxin (20 mg/kg)-induced mortality, plasma levels of arachidonate metabolites and other pathophysiological sequelae in Long-Evans rats. Aspirin, in doses of 3.75, 15 an 30 mg/kg, given 30 min before endotoxin significantly (P less than .01) improved 24-hr survival from 11% to 60 to 70%, but 100 mg/kg afforded no protection. Pretreatment with aspirin (15 or 100 mg/kg) 30 min before endotoxin significantly (P less than .001) decreased the endotoxin-induced elevations in plasma levels of immunoreactive (i) TXB2, a stable metabolite of TXA2, i6-keto PGF1 alpha, a stable metabolite of PGI2 and significantly (P less than .05) inhibited thrombin-induced in vitro platelet iTXB2 synthesis. Endotoxin-induced hypoglycemia and elevations in serum acid phosphatase and beta-glucuronidase activities, lysosomal enzymes, were all significantly (P less than .01) attenuated by pretreatment with aspirin (15 mg/kg) 30 min before endotoxin. Aspirin (15 or 100 mg/kg) given 24 h before challenge with endotoxin significantly improved 24-hr survival to 42 (P less than .01) and 44% (P less than .005), respectively. Although 24 hr pretreatment with aspirin (15 or 100 mg/kg) significantly (P less than .001) reduced endotoxin-induced elevations in iTXB2, only the 100 mg/kg dose significantly lowered plasma levels of i6-keto PGF1 alpha. These observations are consistent with the notion that the beneficial effects of aspirin seen in experimental endotoxic shock may be mediated, in part, via reduction of platelet TXA2 synthesis.