Leukocyte-endothelium interaction in arterioles after ischemia and reperfusion

Leukocyte-endothelium interaction in postcapillary venules plays an important role in reperfusion injury, inflammation, shock, and sepsis. This phenomenon is poorly described in precapillary arterioles. In fact, many researchers have reported no evidence of leukocyte adherence in arterioles whatsoever. Most research has focused on venules of larger rodents, in which observation of the microcirculation, especially arterioles, is limited. We have developed a model which provides a clearer view of these microvessels using the mouse cremaster muscle. This muscle has an approximate thickness of 100 microm allowing images produced by transillumination to be very clear. After vascular isolation, the right cremaster muscle was subjected to 4 h of ischemia, followed by 2 h of reperfusion. The left muscle was not rendered ischemic, thereby allowing it to serve as the animal's own internal control. We observed leukocyte rolling in arterioles in both the ischemic and the nonischemic muscles. Leukocyte sticking was seen in arterioles and venules on both sides, except in control arterioles. The number of rolling and sticking leukocytes on the ischemic side was significantly higher than in controls (P < 0.05) for both arterioles and venules. During the reperfusion period, this number did not change significantly. Transmigration of leukocytes was observed only in venules, but not in arterioles. The number of perfused capillaries was reduced on the ischemic side compared to controls and did not change significantly during the 2 h of reperfusion. Our results demonstrate that leukocyte-endothelium interaction occurs in muscle arterioles of mice. This phenomenon is more pronounced after ischemia and reperfusion, i.e., depends on the extent of tissue insult.