Endotoxin-induced myocardial depression in rats: effect of ibuprofen and SDZ 64-688, a platelet activating factor receptor antagonist

We tested the hypothesis that lipopolysaccharide (LPS)-induced myocardial dysfunction is mediated by cyclooxygenase-derived metabolites of arachidonic acid or platelet activating factor (PAF). Ether-anesthetized rats were injected iv with normal saline (NS; 2.5 ml/kg), ibuprofen (cyclooxygenase inhibitor; 15 mg/kg), or SDZ 64-688 (PAF receptor antagonist; 5 mg/kg). Thirty minutes later, the rats were injected iv with NS (5 ml/kg) or Escherichia coli 0111:B4 LPS (20 mg/kg). Two hours later, atria were harvested, connected to an isometric force transducer-amplifier-recorder apparatus, and maintained in vitro in oxygenated 37.5 degrees C Krebs--Henseleit buffer. Force of contraction indexed to body weight (FOCI; g/kg) was significantly (P less than 0.05) lower in the NS/LPS group (N = 7) than in the NS/NS group (N = 7). Pretreatment with ibuprofen (ibuprofen/LPS group; N = 8) did not affect the adverse effect of LPS on atrial FOCI. In contrast, pretreatment with SDZ 64-688 (64-688/LPS group; N = 8) ameliorated (P less than 0.05) the deleterious effect of LPS on contractility. The PAF antagonist did not manifest intrinsic positive inotropic activity (64-688/NS group; N = 8). These results support the notion that LPS-induced myocardial dysfunction in the rat is mediated, at least in part, by PAF.