P-SELECTIN AND ICAM-1-DEPENDENT ADHERENCE REACTIONS - ROLE IN THE GENESIS OF POSTISCHEMIC NO-REFLOW

The aim of this study was to determine whether immunoneutralization of P-selectin or intercellular adhesion molecule-1 (ICAM-1) (endothelial cell adhesion molecules involved in leukocyte rolling and firm adhesi on, respectively) would attenuate the development of postischemic capi llary no-reflow. Microvascular patency was assessed in vascularly isol ated canine gracilis muscles by perfusion with contrast media (India i nk) at the end of the experimental protocol. Computerized video imagin g was used to quantitate the number of ink-containing microvessels (< 10 mu m diam) per muscle fiber in histological samples obtained from i solated canine gracilis muscles subjected to 4.5 h of continuous perfu sion (nonischemic control), 4 h of ischemia and 30 min of reperfusion (I-R), I-R + P-selectin monoclonal antibodies (MAbs) (MD6 or PB1.3), a nd I-R + ICAM-1 MAbs (CL18/6C7 or R6.5). The efficacy of a P-selectin MAb (MD3) that binds to a nonfunctional epitope was also evaluated. I- R was associated with a marked reduction in the number of patent capil laries per fiber (3.1 +/- 0.2 vs. 1.1 +/- 0.2 patent capillaries/fiber for control and I-R, respectively). Immunoneutralization with MAbs di rected against functional epitopes on P-selectin (MD6 or PB1.3) signif icantly improved capillary perfusion (2.3 +/- 0.3 and 3.6 +/- 0.6 pate nt capillaries/fiber, respectively). On the other hand, MAb MD3, which binds to nonfunctional epitopes on P-selectin, failed to limit the de velopment of postischemic no-reflow (1.0 +/- 0.2 patent capillaries/fi ber). Immunoneutralization of ICAM-1 with CL18/6C7 and R6.5 increased the number of patent capillaries per fiber to 1.8 +/- 0.1 and 2.5 +/- 0.3, respectively. These data indicate that P-selectin and ICAM-1-depe ndent adherence reactions play an important role in the development of the no-reflow phenomenon in postischemic skeletal muscle.