The objective of this study was to examine the effect of nitric oxide (NO) donors on polymorphonuclear leukocyte (PMN) interactions in the microvasculature of postischemic tissue and to compare the antiadhesive properties of NO donors with the responses observed after immunoneutralization of three key adhesion glycoproteins (CD11/CD18, intercellular adhesion molecule-1, and P-selectin). Rolling and firm adhesion (adherence) of leukocytes and shear rate were monitored in cat mesenteric venules subjected to 60 min of ischemia (blood flow reduced to 20% of control), followed by 60 min of reperfusion. Immediately before reperfusion, the mesentery was superfused with a NO donor (3-morpholinosydonimine-N-ethyl-carbamide or spermine-NO) or a monoclonal antibody (MAb) against an adhesion glycoprotein that was administered intravenously. In untreated animals, a profound influx in rolling PMNs was observed during reperfusion that was subsequently followed by increased firm adhesion. The anti-P-selectin antibody completely abolished the rise in the flux of rolling PMNs, whereas the anti-CD18 antibody prevented firm adhesion. Both NO donors attenuated ischemia/reperfusion-induced leukocyte adhesion to a level comparable with that observed after administration of a MAb against CD11/CD18 without affecting PMN rolling. The antiadhesive effect of the NO donors could not be attributed solely to an improvement of venular wall shear rate. In vitro data did not reveal a direct effect of NO donors on the expression of CD18 or neutrophil adhesion to endothelial cells. These observations suggest that NO donors may provide protection from tissue injury by preventing PMN adhesion.(ABSTRACT TRUNCATED AT 250 WORDS)