Effect of complement and arachidonic acid pathway inhibition on white blood cell count and deposition on vascular grafts. To determine the role of complement and arachidonic acid metabolites in the decrease in peripheral white blood cell count (pWBC) observed with graft implantation, Dacron aortic grafts were implanted in control rabbits (Group I, n = 13), or rabbits pretreated with cobra venom factor (80 U/kg) to deplete complement (Group II, n = 13), indomethacin (2.5 mg/kg) to inhibit cyclooxygenase (Group III, n = 7), or diethylcarbamazine (DEC, 90 mg/kg) to inhibit leukotriene synthesis (Group IV, n = 7). pWBC was measured 15 min and 1 hr after graft implantation. After graft removal, the WBC count on grafts (gWBC) was determined by light microscopy (LM) and scanning electron microscopy (SEM). One hr after graft implantation, pWBC decreased significantly in Groups I-IV to 46%, 52%, 40%, and 45% of preoperative pWBC, respectively. There was no significant difference among the groups. LM revealed gWBC per 63x field of 8.0, 12.3, 5.8, and 6.8 in Groups I-IV, respectively. Similarly, SEM showed gWBC per 2000x field of 2.5, 5.6, 0.7, and 1.5 in Groups I-IV, respectively. SEM gWBC was significantly greater in Group II than I (p less than 0.01), and significantly less in Group III than I (p less than 0.05). Results suggested that complement and arachidonic acid pathways alone do not affect the fall in pWBC, but may influence gWBC. 