The objective was to examine the effects of caffeine, dibutyryl cyclic AMP, and heparin on the chemotaxis and/or phagocytosis of PMNs for porcine sperm. The chemotactic activity of PMNs, determined in a blind well chamber, increased (P &lt
0.05) when fresh serum was added to the medium (control containing BSA, 1109.5 cells/mm2 vs serum, 1226.3 cells/mm2), regardless of the presence of sperm (control, 1121.1 cells/mm2 vs serum, 1245.8 cells/mm2), whereas heat-inactivated serum did not affect activity (without sperm, 1099.4 cells/mm2 and with sperm, 1132.6 cells/mm2). Regardless of live and dead sperm and of the origin of PMNs (boars vs sows), the phagocytotic activity of PMNs, as determined by co-culture of PMNs with sperm for 60 min, increased (P &lt
0.05) in the presence of fresh serum containing active complement (46.7 and 43.0%, respectively), but stimulation was decreased (P &lt
0.05) when 1 mM or higher concentrations of caffeine was added to the medium (from 40.7 to 20.8-31.6%). The origin of PMNs (sows vs boars) did not significantly affect phagocytotic activity. The percentage of PMNs that phagocytized polystyrene latex beads decreased when 2 mM caffeine was added to the medium containing porcine serum (from 43.7 to 21.5%). Serum-stimulated chemotactic activity of PMNs (1089.9 cells/mm2) was also reduced (P &lt
0.05) with 2 mM caffeine (942.5 cells/mm2). Furthermore, dibutyryl cAMP at ≥ 0.1 mM or heparin at ≥ 100 μg/mL decreased phagocytotic activity, in a concentration-dependent manner (P &lt
0.05). Supplementation of PMNs with heparin at 100 or 500 μg/mL decreased (P &lt
0.05) chemotactic activity in the presence of serum (from 1137.1 cells/mm2 to 1008.8-1026.3 cells/mm2). We inferred that opsonization in the presence of active complement stimulated phagocytotic and chemotactic activities of PMNs, whereas supplementation with caffeine and dibutyryl cAMP (which could be associated with the intracellular cAMP level of PMNs) or adding heparin decreased serum-stimulated phagocytotic and chemotactic activities. © 2011.