Leucocyte and platelet adhesion in different layers of the small bowel during experimental total warm ischaemia and reperfusion

Background: Ischaemia and reperfusion (IR) of the small bowel is involved in many clinical conditions. A key component in IR-induced tissue damage is microvascular dysfunction. The aim was to investigate the role of leucocytes and platelets in capillary flow impediment and tissue damage. Methods: Anaesthetized rats were subjected to 30 min warm ischaemia of the small bowel, followed by 1 h reperfusion. To elucidate the influence of leucocytes on platelet adhesion, leucocyte-vessel wall interactions induced by IR were prevented by anti-platelet activating factor (PAF) or anti-intercellular adhesion molecule (ICAM)-1. Intravital videomicroscopy was performed and tissue injury was evaluated histologically. Results: In submucosal venules, IR induced an increase in the median number of interacting leucocytes from 3 to 10 and 20 leucocytes per 100-mu m venule segment after 10 and 60 min reperfusion respectively. Anti-PAF or anti-ICAM-1 completely attenuated this increase, resulting in an eightfold improvement in submucosal capillary flow and reduced tissue injury. Shedding of villi no longer occurred. Platelet-vessel wall interactions occurred particularly in submucosal venules, but were not affected by anti-PAF or anti-ICAM-1. Conclusion: Small bowel IR initiated all inflammatory, and thrombotic response in the submucosal layer only. Attenuation of leucocyte adhesion improved submucosal capillary perfusion, preventing shedding of mucosal villi.