Effect of WEB 2086 on leukocyte adherence in response to hemorrhagic shock in rats

Background: The pathogenesis of generalized microvascular injury after hemorrhagic shock is known to involve the generation of platelet-activating factor (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine [PAF]). The release of PAF is manifested in several ways, including by increased vascular permeability, altered vascular reactivity, and increased leukocyte adherence to the endothelium, WEB 2086 is a PAF antagonist that has been shown experimentally to improve survival after hemorrhagic shock. The purpose of this study was to examine the efficacy of WEB 2086 in attenuating leukocyte adherence before, during, and after hemorrhagic shock. Methods: After a control period, blood was withdrawn to reduce the mean arterial pressure to 40 mm Hg for 30 minutes in urethane-anesthetized rats. Mesenteric venules in a transilluminated segment of the small bowel were examined to quantitate leukocyte adherence using intravital microscopy, Results: In sham-operated rats (control), there was minimal to no leukocyte adherence throughout the experiment. Hemorrhagic shock resulted in a significant increase in leukocyte adherence post-shock during resuscitation (10.9 +/- 1.8 cells/100 mum, p < 0.01) when compared with controls. WEB 2086, when given before shock, significantly attenuated leukocyte adherence (0.1 +/- 0.08 cells/100 <mu>m, p < 0.01) when compared with hemorrhagic shock alone. This effect of WEB 2086 on adherence could be demonstrated even when it was given during (3.5 +/- 0.9 cells/100 <mu>m, p < 0.01) and 10 minutes into (5.8 +/- 1.1 cells/100 <mu>m, p < 0.05) hemorrhagic shock. Conclusion: Our findings suggest that WEB 2086 may be of therapeutic benefit against the microvascular damage sustained after hemorrhagic shock.